diff --git a/src/HtmlUtils.tsx b/src/HtmlUtils.tsx
index e8b38d50c5..f925facaf0 100644
--- a/src/HtmlUtils.tsx
+++ b/src/HtmlUtils.tsx
@@ -17,7 +17,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { ReactElement, ReactNode } from "react";
+import React, { LegacyRef, ReactElement, ReactNode } from "react";
 import sanitizeHtml from "sanitize-html";
 import cheerio from "cheerio";
 import classNames from "classnames";
@@ -93,8 +93,8 @@ const MEDIA_API_MXC_REGEX = /\/_matrix\/media\/r0\/(?:download|thumbnail)\/(.+?)
  * positives, but useful for fast-path testing strings to see if they
  * need emojification.
  */
-function mightContainEmoji(str: string): boolean {
-    return SURROGATE_PAIR_PATTERN.test(str) || SYMBOL_PATTERN.test(str);
+function mightContainEmoji(str?: string): boolean {
+    return !!str && (SURROGATE_PAIR_PATTERN.test(str) || SYMBOL_PATTERN.test(str));
 }
 
 /**
@@ -463,7 +463,7 @@ const emojiToJsxSpan = (emoji: string, key: number): JSX.Element => (
  * @returns if isHtmlMessage is true, returns an array of strings, otherwise return an array of React Elements for emojis
  * and plain text for everything else
  */
-function formatEmojis(message: string, isHtmlMessage: boolean): (JSX.Element | string)[] {
+function formatEmojis(message: string | undefined, isHtmlMessage: boolean): (JSX.Element | string)[] {
     const emojiToSpan = isHtmlMessage ? emojiToHtmlSpan : emojiToJsxSpan;
     const result: (JSX.Element | string)[] = [];
     let text = "";
@@ -641,9 +641,9 @@ export function bodyToHtml(content: IContent, highlights: Optional<string[]>, op
  * @return The HTML-ified node.
  */
 export function topicToHtml(
-    topic: string,
+    topic?: string,
     htmlTopic?: string,
-    ref?: React.Ref<HTMLSpanElement>,
+    ref?: LegacyRef<HTMLSpanElement>,
     allowExtendedHtml = false,
 ): ReactNode {
     if (!SettingsStore.getValue("feature_html_topic")) {
diff --git a/src/components/views/auth/CountryDropdown.tsx b/src/components/views/auth/CountryDropdown.tsx
index 4b4396ebb5..fe20730a08 100644
--- a/src/components/views/auth/CountryDropdown.tsx
+++ b/src/components/views/auth/CountryDropdown.tsx
@@ -14,12 +14,13 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React from "react";
+import React, { ReactElement } from "react";
 
 import { COUNTRIES, getEmojiFlag, PhoneNumberCountryDefinition } from "../../../phonenumber";
 import SdkConfig from "../../../SdkConfig";
 import { _t } from "../../../languageHandler";
 import Dropdown from "../elements/Dropdown";
+import { NonEmptyArray } from "../../../@types/common";
 
 const COUNTRIES_BY_ISO2: Record<string, PhoneNumberCountryDefinition> = {};
 for (const c of COUNTRIES) {
@@ -131,7 +132,7 @@ export default class CountryDropdown extends React.Component<IProps, IState> {
                     {_t(country.name)} (+{country.prefix})
                 </div>
             );
-        });
+        }) as NonEmptyArray<ReactElement & { key: string }>;
 
         // default value here too, otherwise we need to handle null / undefined
         // values between mounting and the initial value propagating
diff --git a/src/components/views/dialogs/AddExistingToSpaceDialog.tsx b/src/components/views/dialogs/AddExistingToSpaceDialog.tsx
index 9fe0ca865b..9156e1b2e0 100644
--- a/src/components/views/dialogs/AddExistingToSpaceDialog.tsx
+++ b/src/components/views/dialogs/AddExistingToSpaceDialog.tsx
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { ReactNode, useContext, useMemo, useRef, useState } from "react";
+import React, { ReactElement, ReactNode, useContext, useMemo, useRef, useState } from "react";
 import classNames from "classnames";
 import { Room } from "matrix-js-sdk/src/models/room";
 import { sleep } from "matrix-js-sdk/src/utils";
@@ -41,6 +41,7 @@ import QueryMatcher from "../../../autocomplete/QueryMatcher";
 import LazyRenderList from "../elements/LazyRenderList";
 import { useSettingValue } from "../../../hooks/useSettings";
 import { filterBoolean } from "../../../utils/arrays";
+import { NonEmptyArray } from "../../../@types/common";
 
 // These values match CSS
 const ROW_HEIGHT = 32 + 12;
@@ -415,17 +416,19 @@ export const SubspaceSelector: React.FC<ISubspaceSelectorProps> = ({ title, spac
                 value={value.roomId}
                 label={_t("Space selection")}
             >
-                {options.map((space) => {
-                    const classes = classNames({
-                        mx_SubspaceSelector_dropdownOptionActive: space === value,
-                    });
-                    return (
-                        <div key={space.roomId} className={classes}>
-                            <RoomAvatar room={space} width={24} height={24} />
-                            {space.name || getDisplayAliasForRoom(space) || space.roomId}
-                        </div>
-                    );
-                })}
+                {
+                    options.map((space) => {
+                        const classes = classNames({
+                            mx_SubspaceSelector_dropdownOptionActive: space === value,
+                        });
+                        return (
+                            <div key={space.roomId} className={classes}>
+                                <RoomAvatar room={space} width={24} height={24} />
+                                {space.name || getDisplayAliasForRoom(space) || space.roomId}
+                            </div>
+                        );
+                    }) as NonEmptyArray<ReactElement & { key: string }>
+                }
             </Dropdown>
         );
     } else {
diff --git a/src/components/views/elements/AppPermission.tsx b/src/components/views/elements/AppPermission.tsx
index 7adae9113b..23187850d4 100644
--- a/src/components/views/elements/AppPermission.tsx
+++ b/src/components/views/elements/AppPermission.tsx
@@ -40,7 +40,7 @@ interface IProps {
 interface IState {
     roomMember: RoomMember;
     isWrapped: boolean;
-    widgetDomain: string;
+    widgetDomain: string | null;
 }
 
 export default class AppPermission extends React.Component<IProps, IState> {
@@ -66,14 +66,14 @@ export default class AppPermission extends React.Component<IProps, IState> {
         };
     }
 
-    private parseWidgetUrl(): { isWrapped: boolean; widgetDomain: string } {
+    private parseWidgetUrl(): { isWrapped: boolean; widgetDomain: string | null } {
         const widgetUrl = url.parse(this.props.url);
-        const params = new URLSearchParams(widgetUrl.search);
+        const params = new URLSearchParams(widgetUrl.search ?? undefined);
 
         // HACK: We're relying on the query params when we should be relying on the widget's `data`.
         // This is a workaround for Scalar.
-        if (WidgetUtils.isScalarUrl(this.props.url) && params && params.get("url")) {
-            const unwrappedUrl = url.parse(params.get("url"));
+        if (WidgetUtils.isScalarUrl(this.props.url) && params?.get("url")) {
+            const unwrappedUrl = url.parse(params.get("url")!);
             return {
                 widgetDomain: unwrappedUrl.host || unwrappedUrl.hostname,
                 isWrapped: true,
diff --git a/src/components/views/elements/AppTile.tsx b/src/components/views/elements/AppTile.tsx
index 01629c5d5c..bf1ccb35d1 100644
--- a/src/components/views/elements/AppTile.tsx
+++ b/src/components/views/elements/AppTile.tsx
@@ -586,7 +586,7 @@ export default class AppTile extends React.Component<IProps, IState> {
                     <AppWarning errorMsg={_t("Error loading Widget")} />
                 </div>
             );
-        } else if (!this.state.hasPermissionToLoad) {
+        } else if (!this.state.hasPermissionToLoad && this.props.room) {
             // only possible for room widgets, can assert this.props.room here
             const isEncrypted = this.context.isRoomEncrypted(this.props.room.roomId);
             appTileBody = (
@@ -689,11 +689,9 @@ export default class AppTile extends React.Component<IProps, IState> {
 
         const layoutButtons: ReactNode[] = [];
         if (this.props.showLayoutButtons) {
-            const isMaximised = WidgetLayoutStore.instance.isInContainer(
-                this.props.room,
-                this.props.app,
-                Container.Center,
-            );
+            const isMaximised =
+                this.props.room &&
+                WidgetLayoutStore.instance.isInContainer(this.props.room, this.props.app, Container.Center);
             const maximisedClasses = classNames({
                 mx_AppTileMenuBar_iconButton: true,
                 mx_AppTileMenuBar_iconButton_collapse: isMaximised,
diff --git a/src/components/views/elements/DesktopCapturerSourcePicker.tsx b/src/components/views/elements/DesktopCapturerSourcePicker.tsx
index cc1b7d1ffd..b34f951af3 100644
--- a/src/components/views/elements/DesktopCapturerSourcePicker.tsx
+++ b/src/components/views/elements/DesktopCapturerSourcePicker.tsx
@@ -123,7 +123,7 @@ export default class DesktopCapturerSourcePicker extends React.Component<PickerI
     };
 
     private onShare = (): void => {
-        this.props.onFinished(this.state.selectedSource.id);
+        this.props.onFinished(this.state.selectedSource?.id);
     };
 
     private onTabChange = (): void => {
diff --git a/src/components/views/elements/Dropdown.tsx b/src/components/views/elements/Dropdown.tsx
index e16eaf978e..f603a4b957 100644
--- a/src/components/views/elements/Dropdown.tsx
+++ b/src/components/views/elements/Dropdown.tsx
@@ -23,6 +23,7 @@ import { _t } from "../../../languageHandler";
 import { getKeyBindingsManager } from "../../../KeyBindingsManager";
 import { KeyBindingAction } from "../../../accessibility/KeyboardShortcuts";
 import { objectHasDiff } from "../../../utils/objects";
+import { NonEmptyArray } from "../../../@types/common";
 
 interface IMenuOptionProps {
     children: ReactElement;
@@ -77,7 +78,7 @@ export interface DropdownProps {
     label: string;
     value?: string;
     className?: string;
-    children: ReactElement[];
+    children: NonEmptyArray<ReactElement & { key: string }>;
     // negative for consistency with HTML
     disabled?: boolean;
     // The width that the dropdown should be. If specified,
@@ -102,7 +103,7 @@ export interface DropdownProps {
 
 interface IState {
     expanded: boolean;
-    highlightedOption: string | null;
+    highlightedOption: string;
     searchQuery: string;
 }
 
@@ -122,14 +123,14 @@ export default class Dropdown extends React.Component<DropdownProps, IState> {
 
         this.reindexChildren(this.props.children);
 
-        const firstChild = React.Children.toArray(props.children)[0] as ReactElement;
+        const firstChild = props.children[0];
 
         this.state = {
             // True if the menu is dropped-down
             expanded: false,
             // The key of the highlighted option
             // (the option that would become selected if you pressed enter)
-            highlightedOption: firstChild ? (firstChild.key as string) : null,
+            highlightedOption: firstChild.key,
             // the current search query
             searchQuery: "",
         };
@@ -144,7 +145,7 @@ export default class Dropdown extends React.Component<DropdownProps, IState> {
             this.reindexChildren(this.props.children);
             const firstChild = this.props.children[0];
             this.setState({
-                highlightedOption: String(firstChild?.key) ?? null,
+                highlightedOption: firstChild.key,
             });
         }
     }
@@ -156,7 +157,7 @@ export default class Dropdown extends React.Component<DropdownProps, IState> {
     private reindexChildren(children: ReactElement[]): void {
         this.childrenByKey = {};
         React.Children.forEach(children, (child) => {
-            this.childrenByKey[child.key] = child;
+            this.childrenByKey[(child as DropdownProps["children"][number]).key] = child;
         });
     }
 
@@ -291,13 +292,11 @@ export default class Dropdown extends React.Component<DropdownProps, IState> {
         return keys[index <= 0 ? keys.length - 1 : (index - 1) % keys.length];
     }
 
-    private scrollIntoView(node: Element): void {
-        if (node) {
-            node.scrollIntoView({
-                block: "nearest",
-                behavior: "auto",
-            });
-        }
+    private scrollIntoView(node: Element | null): void {
+        node?.scrollIntoView({
+            block: "nearest",
+            behavior: "auto",
+        });
     }
 
     private getMenuOptions(): JSX.Element[] {
@@ -317,7 +316,7 @@ export default class Dropdown extends React.Component<DropdownProps, IState> {
                 </MenuOption>
             );
         });
-        if (options.length === 0) {
+        if (!options?.length) {
             return [
                 <div key="0" className="mx_Dropdown_option" role="option" aria-selected={false}>
                     {_t("No results")}
@@ -363,9 +362,13 @@ export default class Dropdown extends React.Component<DropdownProps, IState> {
         }
 
         if (!currentValue) {
-            const selectedChild = this.props.getShortOption
-                ? this.props.getShortOption(this.props.value)
-                : this.childrenByKey[this.props.value];
+            let selectedChild: ReactNode | undefined;
+            if (this.props.value) {
+                selectedChild = this.props.getShortOption
+                    ? this.props.getShortOption(this.props.value)
+                    : this.childrenByKey[this.props.value];
+            }
+
             currentValue = (
                 <div className="mx_Dropdown_option" id={`${this.props.id}_value`}>
                     {selectedChild || this.props.placeholder}
diff --git a/src/components/views/elements/EditableText.tsx b/src/components/views/elements/EditableText.tsx
index 5c11e52ecc..4e2f228a84 100644
--- a/src/components/views/elements/EditableText.tsx
+++ b/src/components/views/elements/EditableText.tsx
@@ -87,6 +87,7 @@ export default class EditableText extends React.Component<IProps, IState> {
     }
 
     private showPlaceholder = (show: boolean): void => {
+        if (!this.editableDiv.current) return;
         if (show) {
             this.editableDiv.current.textContent = this.props.placeholder;
             this.editableDiv.current.setAttribute(
@@ -134,7 +135,7 @@ export default class EditableText extends React.Component<IProps, IState> {
         if (!(ev.target as HTMLDivElement).textContent) {
             this.showPlaceholder(true);
         } else if (!this.placeholder) {
-            this.value = (ev.target as HTMLDivElement).textContent;
+            this.value = (ev.target as HTMLDivElement).textContent ?? "";
         }
 
         const action = getKeyBindingsManager().getAccessibilityAction(ev);
@@ -163,7 +164,7 @@ export default class EditableText extends React.Component<IProps, IState> {
             range.setStart(node, 0);
             range.setEnd(node, ev.target.childNodes.length);
 
-            const sel = window.getSelection();
+            const sel = window.getSelection()!;
             sel.removeAllRanges();
             sel.addRange(range);
         }
@@ -190,7 +191,7 @@ export default class EditableText extends React.Component<IProps, IState> {
     };
 
     private onBlur = (ev: React.FocusEvent<HTMLDivElement>): void => {
-        const sel = window.getSelection();
+        const sel = window.getSelection()!;
         sel.removeAllRanges();
 
         if (this.props.blurToCancel) {
diff --git a/src/components/views/elements/EffectsOverlay.tsx b/src/components/views/elements/EffectsOverlay.tsx
index 604b513d30..11e11211b2 100644
--- a/src/components/views/elements/EffectsOverlay.tsx
+++ b/src/components/views/elements/EffectsOverlay.tsx
@@ -54,14 +54,14 @@ const EffectsOverlay: FunctionComponent<IProps> = ({ roomWidth }) => {
         };
         const onAction = (payload: { action: string }): void => {
             const actionPrefix = "effects.";
-            if (payload.action.indexOf(actionPrefix) === 0) {
+            if (canvasRef.current && payload.action.startsWith(actionPrefix)) {
                 const effect = payload.action.slice(actionPrefix.length);
-                lazyLoadEffectModule(effect).then((module) => module?.start(canvasRef.current));
+                lazyLoadEffectModule(effect).then((module) => module?.start(canvasRef.current!));
             }
         };
         const dispatcherRef = dis.register(onAction);
         const canvas = canvasRef.current;
-        canvas.height = UIStore.instance.windowHeight;
+        if (canvas) canvas.height = UIStore.instance.windowHeight;
         UIStore.instance.on(UI_EVENTS.Resize, resize);
 
         return () => {
diff --git a/src/components/views/elements/EventListSummary.tsx b/src/components/views/elements/EventListSummary.tsx
index 882e68c9f8..1fc44e5f90 100644
--- a/src/components/views/elements/EventListSummary.tsx
+++ b/src/components/views/elements/EventListSummary.tsx
@@ -78,7 +78,9 @@ enum TransitionType {
 
 const SEP = ",";
 
-export default class EventListSummary extends React.Component<IProps> {
+export default class EventListSummary extends React.Component<
+    IProps & Required<Pick<IProps, "summaryLength" | "threshold" | "avatarsMaxLength" | "layout">>
+> {
     public static contextType = RoomContext;
     public context!: React.ContextType<typeof RoomContext>;
 
@@ -508,12 +510,12 @@ export default class EventListSummary extends React.Component<IProps> {
             const type = e.getType();
 
             let userKey = e.getSender()!;
-            if (type === EventType.RoomThirdPartyInvite) {
+            if (e.isState() && type === EventType.RoomThirdPartyInvite) {
                 userKey = e.getContent().display_name;
-            } else if (type === EventType.RoomMember) {
-                userKey = e.getStateKey();
-            } else if (e.isRedacted()) {
-                userKey = e.getUnsigned()?.redacted_because?.sender;
+            } else if (e.isState() && type === EventType.RoomMember) {
+                userKey = e.getStateKey()!;
+            } else if (e.isRedacted() && e.getUnsigned()?.redacted_because) {
+                userKey = e.getUnsigned().redacted_because!.sender;
             }
 
             // Initialise a user's events
diff --git a/src/components/views/elements/Field.tsx b/src/components/views/elements/Field.tsx
index c5e531360f..96151a2e96 100644
--- a/src/components/views/elements/Field.tsx
+++ b/src/components/views/elements/Field.tsx
@@ -38,8 +38,6 @@ export interface IValidateOpts {
 interface IProps {
     // The field's ID, which binds the input and label together. Immutable.
     id?: string;
-    // id of a <datalist> element for suggestions
-    list?: string;
     // The field's label string.
     label?: string;
     // The field's placeholder string. Defaults to the label.
@@ -119,7 +117,7 @@ interface IState {
 }
 
 export default class Field extends React.PureComponent<PropShapes, IState> {
-    private id: string;
+    private readonly id: string;
     private inputRef: RefObject<HTMLInputElement | HTMLSelectElement | HTMLTextAreaElement>;
 
     public static readonly defaultProps = {
@@ -243,7 +241,6 @@ export default class Field extends React.PureComponent<PropShapes, IState> {
             tooltipContent,
             forceValidity,
             tooltipClassName,
-            list,
             validateOnBlur,
             validateOnChange,
             validateOnFocus,
@@ -262,7 +259,11 @@ export default class Field extends React.PureComponent<PropShapes, IState> {
         inputProps.onBlur = this.onBlur;
 
         // Appease typescript's inference
-        const inputProps_ = { ...inputProps, ref: this.inputRef, list };
+        const inputProps_: React.HTMLAttributes<HTMLSelectElement | HTMLInputElement | HTMLTextAreaElement> &
+            React.ClassAttributes<HTMLSelectElement | HTMLInputElement | HTMLTextAreaElement> = {
+            ...inputProps,
+            ref: this.inputRef,
+        };
 
         const fieldInput = React.createElement(this.props.element, inputProps_, children);
 
@@ -287,7 +288,7 @@ export default class Field extends React.PureComponent<PropShapes, IState> {
         });
 
         // Handle displaying feedback on validity
-        let fieldTooltip;
+        let fieldTooltip: JSX.Element | undefined;
         if (tooltipContent || this.state.feedback) {
             let role: React.AriaRole;
             if (tooltipContent) {
diff --git a/src/components/views/elements/FilterDropdown.tsx b/src/components/views/elements/FilterDropdown.tsx
index 80ca10ebdc..8dd5b0173d 100644
--- a/src/components/views/elements/FilterDropdown.tsx
+++ b/src/components/views/elements/FilterDropdown.tsx
@@ -14,11 +14,12 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React from "react";
+import React, { ReactElement } from "react";
 import classNames from "classnames";
 
 import { Icon as CheckmarkIcon } from "../../../../res/img/element-icons/roomlist/checkmark.svg";
 import Dropdown, { DropdownProps } from "./Dropdown";
+import { NonEmptyArray } from "../../../@types/common";
 
 export type FilterDropdownOption<FilterKeysType extends string> = {
     id: FilterKeysType;
@@ -63,13 +64,15 @@ export const FilterDropdown = <FilterKeysType extends string = string>({
             className={classNames("mx_FilterDropdown", className)}
             getShortOption={getSelectedFilterOptionComponent<FilterKeysType>(options, selectedLabel)}
         >
-            {options.map(({ id, label, description }) => (
-                <div className="mx_FilterDropdown_option" data-testid={`filter-option-${id}`} key={id}>
-                    {id === value && <CheckmarkIcon className="mx_FilterDropdown_optionSelectedIcon" />}
-                    <span className="mx_FilterDropdown_optionLabel">{label}</span>
-                    {!!description && <span className="mx_FilterDropdown_optionDescription">{description}</span>}
-                </div>
-            ))}
+            {
+                options.map(({ id, label, description }) => (
+                    <div className="mx_FilterDropdown_option" data-testid={`filter-option-${id}`} key={id}>
+                        {id === value && <CheckmarkIcon className="mx_FilterDropdown_optionSelectedIcon" />}
+                        <span className="mx_FilterDropdown_optionLabel">{label}</span>
+                        {!!description && <span className="mx_FilterDropdown_optionDescription">{description}</span>}
+                    </div>
+                )) as NonEmptyArray<ReactElement & { key: string }>
+            }
         </Dropdown>
     );
 };
diff --git a/src/components/views/elements/ImageView.tsx b/src/components/views/elements/ImageView.tsx
index 6118e02317..aa8f82bb03 100644
--- a/src/components/views/elements/ImageView.tsx
+++ b/src/components/views/elements/ImageView.tsx
@@ -96,17 +96,24 @@ export default class ImageView extends React.Component<IProps, IState> {
 
         const { thumbnailInfo } = this.props;
 
+        let translationX = 0;
+        let translationY = 0;
+        if (thumbnailInfo) {
+            translationX = thumbnailInfo.positionX + thumbnailInfo.width / 2 - UIStore.instance.windowWidth / 2;
+            translationY =
+                thumbnailInfo.positionY +
+                thumbnailInfo.height / 2 -
+                UIStore.instance.windowHeight / 2 -
+                getPanelHeight() / 2;
+        }
+
         this.state = {
             zoom: 0, // We default to 0 and override this in imageLoaded once we have naturalSize
             minZoom: MAX_SCALE,
             maxZoom: MAX_SCALE,
             rotation: 0,
-            translationX: thumbnailInfo?.positionX + thumbnailInfo?.width / 2 - UIStore.instance.windowWidth / 2 ?? 0,
-            translationY:
-                thumbnailInfo?.positionY +
-                    thumbnailInfo?.height / 2 -
-                    UIStore.instance.windowHeight / 2 -
-                    getPanelHeight() / 2 ?? 0,
+            translationX,
+            translationY,
             moving: false,
             contextMenuDisplayed: false,
         };
@@ -143,6 +150,7 @@ export default class ImageView extends React.Component<IProps, IState> {
     }
 
     private imageLoaded = (): void => {
+        if (!this.image.current) return;
         // First, we calculate the zoom, so that the image has the same size as
         // the thumbnail
         const { thumbnailInfo } = this.props;
@@ -226,22 +234,23 @@ export default class ImageView extends React.Component<IProps, IState> {
                 translationX: 0,
                 translationY: 0,
             });
-        } else if (typeof anchorX !== "number" && typeof anchorY !== "number") {
+        } else if (typeof anchorX !== "number" || typeof anchorY !== "number") {
             // Zoom relative to the center of the view
             this.setState({
                 zoom: newZoom,
                 translationX: (this.state.translationX * newZoom) / oldZoom,
                 translationY: (this.state.translationY * newZoom) / oldZoom,
             });
-        } else {
+        } else if (this.image.current) {
             // Zoom relative to the given point on the image.
             // First we need to figure out the offset of the anchor point
             // relative to the center of the image, accounting for rotation.
-            let offsetX: number | undefined;
-            let offsetY: number | undefined;
+            let offsetX: number;
+            let offsetY: number;
             // The modulo operator can return negative values for some
             // rotations, so we have to do some extra work to normalize it
-            switch (((this.state.rotation % 360) + 360) % 360) {
+            const rotation = (((this.state.rotation % 360) + 360) % 360) as 0 | 90 | 180 | 270;
+            switch (rotation) {
                 case 0:
                     offsetX = this.image.current.clientWidth / 2 - anchorX;
                     offsetY = this.image.current.clientHeight / 2 - anchorY;
@@ -384,7 +393,7 @@ export default class ImageView extends React.Component<IProps, IState> {
     private onEndMoving = (): void => {
         // Zoom out if we haven't moved much
         if (
-            this.state.moving === true &&
+            this.state.moving &&
             Math.abs(this.state.translationX - this.previousX) < ZOOM_DISTANCE &&
             Math.abs(this.state.translationY - this.previousY) < ZOOM_DISTANCE
         ) {
@@ -397,7 +406,7 @@ export default class ImageView extends React.Component<IProps, IState> {
 
     private renderContextMenu(): JSX.Element {
         let contextMenu: JSX.Element | undefined;
-        if (this.state.contextMenuDisplayed) {
+        if (this.state.contextMenuDisplayed && this.props.mxEvent) {
             contextMenu = (
                 <MessageContextMenu
                     {...aboveLeftOf(this.contextMenuButton.current.getBoundingClientRect())}
@@ -445,7 +454,7 @@ export default class ImageView extends React.Component<IProps, IState> {
             const showTwelveHour = SettingsStore.getValue("showTwelveHourTimestamps");
             let permalink = "#";
             if (this.props.permalinkCreator) {
-                permalink = this.props.permalinkCreator.forEvent(mxEvent.getId());
+                permalink = this.props.permalinkCreator.forEvent(mxEvent.getId()!);
             }
 
             const senderName = mxEvent.sender?.name ?? mxEvent.getSender();
diff --git a/src/components/views/elements/InteractiveTooltip.tsx b/src/components/views/elements/InteractiveTooltip.tsx
index 3aecd8a743..c862f06d95 100644
--- a/src/components/views/elements/InteractiveTooltip.tsx
+++ b/src/components/views/elements/InteractiveTooltip.tsx
@@ -378,6 +378,7 @@ export default class InteractiveTooltip extends React.Component<IProps, IState>
     private onMouseMove = (ev: MouseEvent): void => {
         const { clientX: x, clientY: y } = ev;
         const { contentRect } = this.state;
+        if (!contentRect) return;
         const targetRect = this.target.getBoundingClientRect();
 
         let direction: Direction;
diff --git a/src/components/views/elements/JoinRuleDropdown.tsx b/src/components/views/elements/JoinRuleDropdown.tsx
index 99d2780a49..36e68bf459 100644
--- a/src/components/views/elements/JoinRuleDropdown.tsx
+++ b/src/components/views/elements/JoinRuleDropdown.tsx
@@ -14,10 +14,11 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React from "react";
+import React, { ReactElement } from "react";
 import { JoinRule } from "matrix-js-sdk/src/@types/partials";
 
 import Dropdown from "./Dropdown";
+import { NonEmptyArray } from "../../../@types/common";
 
 interface IProps {
     value: JoinRule;
@@ -45,13 +46,15 @@ const JoinRuleDropdown: React.FC<IProps> = ({
         <div key={JoinRule.Public} className="mx_JoinRuleDropdown_public">
             {labelPublic}
         </div>,
-    ];
+    ] as NonEmptyArray<ReactElement & { key: string }>;
 
     if (labelRestricted) {
         options.unshift(
-            <div key={JoinRule.Restricted} className="mx_JoinRuleDropdown_restricted">
-                {labelRestricted}
-            </div>,
+            (
+                <div key={JoinRule.Restricted} className="mx_JoinRuleDropdown_restricted">
+                    {labelRestricted}
+                </div>
+            ) as ReactElement & { key: string },
         );
     }
 
diff --git a/src/components/views/elements/LanguageDropdown.tsx b/src/components/views/elements/LanguageDropdown.tsx
index 178d85c4eb..5de1ffe785 100644
--- a/src/components/views/elements/LanguageDropdown.tsx
+++ b/src/components/views/elements/LanguageDropdown.tsx
@@ -15,13 +15,14 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React from "react";
+import React, { ReactElement } from "react";
 
 import * as languageHandler from "../../../languageHandler";
 import SettingsStore from "../../../settings/SettingsStore";
 import { _t } from "../../../languageHandler";
 import Spinner from "./Spinner";
 import Dropdown from "./Dropdown";
+import { NonEmptyArray } from "../../../@types/common";
 
 type Languages = Awaited<ReturnType<typeof languageHandler.getAllLanguagesFromJson>>;
 
@@ -99,7 +100,7 @@ export default class LanguageDropdown extends React.Component<IProps, IState> {
 
         const options = displayedLanguages.map((language) => {
             return <div key={language.value}>{language.label}</div>;
-        });
+        }) as NonEmptyArray<ReactElement & { key: string }>;
 
         // default value here too, otherwise we need to handle null / undefined
         // values between mounting and the initial value propagating
diff --git a/src/components/views/elements/MiniAvatarUploader.tsx b/src/components/views/elements/MiniAvatarUploader.tsx
index 18652a4c62..464c89ba23 100644
--- a/src/components/views/elements/MiniAvatarUploader.tsx
+++ b/src/components/views/elements/MiniAvatarUploader.tsx
@@ -16,7 +16,7 @@ limitations under the License.
 
 import classNames from "classnames";
 import { EventType } from "matrix-js-sdk/src/@types/event";
-import React, { useContext, useRef, useState, MouseEvent, ReactNode } from "react";
+import React, { useContext, useRef, useState, MouseEvent, ReactNode, RefObject } from "react";
 
 import MatrixClientContext from "../../../contexts/MatrixClientContext";
 import RoomContext from "../../../contexts/RoomContext";
@@ -59,7 +59,7 @@ const MiniAvatarUploader: React.FC<IProps> = ({
         setShow(false);
     }, 13000); // hide after being shown for 10 seconds
 
-    const uploadRef = useRef<HTMLInputElement>();
+    const uploadRef = useRef() as RefObject<HTMLInputElement>;
 
     const label = hasAvatar || busy ? hasAvatarLabel : noAvatarLabel;
 
@@ -97,7 +97,7 @@ const MiniAvatarUploader: React.FC<IProps> = ({
                 })}
                 disabled={busy}
                 onClick={() => {
-                    uploadRef.current.click();
+                    uploadRef.current?.click();
                 }}
                 onMouseOver={() => setHover(true)}
                 onMouseLeave={() => setHover(false)}
diff --git a/src/components/views/elements/ReplyChain.tsx b/src/components/views/elements/ReplyChain.tsx
index e4a720ce4c..6409464701 100644
--- a/src/components/views/elements/ReplyChain.tsx
+++ b/src/components/views/elements/ReplyChain.tsx
@@ -31,7 +31,7 @@ import { Action } from "../../../dispatcher/actions";
 import Spinner from "./Spinner";
 import ReplyTile from "../rooms/ReplyTile";
 import { Pill, PillType } from "./Pill";
-import AccessibleButton, { ButtonEvent } from "./AccessibleButton";
+import AccessibleButton from "./AccessibleButton";
 import { getParentEventId, shouldDisplayReply } from "../../../utils/Reply";
 import RoomContext from "../../../contexts/RoomContext";
 import { MatrixClientPeg } from "../../../MatrixClientPeg";
@@ -45,7 +45,7 @@ const SHOW_EXPAND_QUOTE_PIXELS = 60;
 
 interface IProps {
     // the latest event in this chain of replies
-    parentEv?: MatrixEvent;
+    parentEv: MatrixEvent;
     // called when the ReplyChain contents has changed, including EventTiles thereof
     onHeightChanged: () => void;
     permalinkCreator?: RoomPermalinkCreator;
@@ -91,7 +91,7 @@ export default class ReplyChain extends React.Component<IProps, IState> {
             err: false,
         };
 
-        this.room = this.matrixClient.getRoom(this.props.parentEv.getRoomId());
+        this.room = this.matrixClient.getRoom(this.props.parentEv.getRoomId())!;
     }
 
     private get matrixClient(): MatrixClient {
@@ -155,7 +155,7 @@ export default class ReplyChain extends React.Component<IProps, IState> {
         }
     }
 
-    private async getEvent(eventId: string): Promise<MatrixEvent | null> {
+    private async getEvent(eventId?: string): Promise<MatrixEvent | null> {
         if (!eventId) return null;
         const event = this.room.findEventById(eventId);
         if (event) return event;
@@ -180,7 +180,8 @@ export default class ReplyChain extends React.Component<IProps, IState> {
         this.initialize();
     };
 
-    private onQuoteClick = async (event: ButtonEvent): Promise<void> => {
+    private onQuoteClick = async (): Promise<void> => {
+        if (!this.state.loadedEv) return;
         const events = [this.state.loadedEv, ...this.state.events];
 
         let loadedEv: MatrixEvent | null = null;
diff --git a/src/components/views/elements/RoomTopic.tsx b/src/components/views/elements/RoomTopic.tsx
index 7aa6bce949..ad59012c78 100644
--- a/src/components/views/elements/RoomTopic.tsx
+++ b/src/components/views/elements/RoomTopic.tsx
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { useCallback, useContext, useRef } from "react";
+import React, { RefObject, useCallback, useContext, useRef } from "react";
 import { Room } from "matrix-js-sdk/src/models/room";
 import classNames from "classnames";
 import { EventType } from "matrix-js-sdk/src/@types/event";
@@ -38,7 +38,7 @@ interface IProps extends React.HTMLProps<HTMLDivElement> {
 
 export default function RoomTopic({ room, ...props }: IProps): JSX.Element {
     const client = useContext(MatrixClientContext);
-    const ref = useRef<HTMLDivElement>();
+    const ref = useRef() as RefObject<HTMLDivElement>;
 
     const topic = useTopic(room);
     const body = topicToHtml(topic?.text, topic?.html, ref);
diff --git a/src/components/views/elements/SpellCheckLanguagesDropdown.tsx b/src/components/views/elements/SpellCheckLanguagesDropdown.tsx
index 7a725cf2d4..3689e8b2ec 100644
--- a/src/components/views/elements/SpellCheckLanguagesDropdown.tsx
+++ b/src/components/views/elements/SpellCheckLanguagesDropdown.tsx
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React from "react";
+import React, { ReactElement } from "react";
 
 import Dropdown from "../../views/elements/Dropdown";
 import PlatformPeg from "../../../PlatformPeg";
@@ -22,6 +22,7 @@ import SettingsStore from "../../../settings/SettingsStore";
 import { _t } from "../../../languageHandler";
 import Spinner from "./Spinner";
 import * as languageHandler from "../../../languageHandler";
+import { NonEmptyArray } from "../../../@types/common";
 
 type Languages = Awaited<ReturnType<typeof languageHandler.getAllLanguagesFromJson>>;
 function languageMatchesSearchQuery(query: string, language: Languages[0]): boolean {
@@ -106,7 +107,7 @@ export default class SpellCheckLanguagesDropdown extends React.Component<
 
         const options = displayedLanguages.map((language) => {
             return <div key={language.value}>{language.label}</div>;
-        });
+        }) as NonEmptyArray<ReactElement & { key: string }>;
 
         // default value here too, otherwise we need to handle null / undefined;
         // values between mounting and the initial value propagating
diff --git a/src/components/views/location/LiveDurationDropdown.tsx b/src/components/views/location/LiveDurationDropdown.tsx
index 6c7a7a14ec..fbb88ca6bc 100644
--- a/src/components/views/location/LiveDurationDropdown.tsx
+++ b/src/components/views/location/LiveDurationDropdown.tsx
@@ -14,11 +14,12 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React from "react";
+import React, { ReactElement } from "react";
 
 import { formatDuration } from "../../../DateUtils";
 import { _t } from "../../../languageHandler";
 import Dropdown from "../elements/Dropdown";
+import { NonEmptyArray } from "../../../@types/common";
 
 const DURATION_MS = {
     fifteenMins: 900000,
@@ -68,11 +69,13 @@ const LiveDurationDropdown: React.FC<Props> = ({ timeout, onChange }) => {
             onOptionChange={onOptionChange}
             className="mx_LiveDurationDropdown"
         >
-            {options.map(({ key, label }) => (
-                <div data-test-id={`live-duration-option-${key}`} key={key}>
-                    {label}
-                </div>
-            ))}
+            {
+                options.map(({ key, label }) => (
+                    <div data-test-id={`live-duration-option-${key}`} key={key}>
+                        {label}
+                    </div>
+                )) as NonEmptyArray<ReactElement & { key: string }>
+            }
         </Dropdown>
     );
 };
diff --git a/src/components/views/spaces/QuickThemeSwitcher.tsx b/src/components/views/spaces/QuickThemeSwitcher.tsx
index b68783a795..500588e9ed 100644
--- a/src/components/views/spaces/QuickThemeSwitcher.tsx
+++ b/src/components/views/spaces/QuickThemeSwitcher.tsx
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { useMemo } from "react";
+import React, { ReactElement, useMemo } from "react";
 
 import { _t } from "../../../languageHandler";
 import { Action } from "../../../dispatcher/actions";
@@ -26,6 +26,7 @@ import { SettingLevel } from "../../../settings/SettingLevel";
 import dis from "../../../dispatcher/dispatcher";
 import { RecheckThemePayload } from "../../../dispatcher/payloads/RecheckThemePayload";
 import PosthogTrackers from "../../../PosthogTrackers";
+import { NonEmptyArray } from "../../../@types/common";
 
 type Props = {
     requestClose: () => void;
@@ -86,9 +87,11 @@ const QuickThemeSwitcher: React.FC<Props> = ({ requestClose }) => {
                 value={selectedTheme}
                 label={_t("Space selection")}
             >
-                {themeOptions.map((theme) => (
-                    <div key={theme.id}>{theme.name}</div>
-                ))}
+                {
+                    themeOptions.map((theme) => <div key={theme.id}>{theme.name}</div>) as NonEmptyArray<
+                        ReactElement & { key: string }
+                    >
+                }
             </Dropdown>
         </div>
     );
diff --git a/test/components/views/elements/EventListSummary-test.tsx b/test/components/views/elements/EventListSummary-test.tsx
index 3fcec7d6d8..03c01c453e 100644
--- a/test/components/views/elements/EventListSummary-test.tsx
+++ b/test/components/views/elements/EventListSummary-test.tsx
@@ -118,7 +118,10 @@ describe("EventListSummary", function () {
         ...mockClientMethodsUser(),
     });
 
-    const defaultProps: ComponentProps<typeof EventListSummary> = {
+    const defaultProps: Omit<
+        ComponentProps<typeof EventListSummary>,
+        "summaryLength" | "threshold" | "avatarsMaxLength"
+    > = {
         layout: Layout.Bubble,
         events: [],
         children: [],
diff --git a/test/components/views/elements/__snapshots__/FilterDropdown-test.tsx.snap b/test/components/views/elements/__snapshots__/FilterDropdown-test.tsx.snap
index 627c92f3eb..d82ee64cef 100644
--- a/test/components/views/elements/__snapshots__/FilterDropdown-test.tsx.snap
+++ b/test/components/views/elements/__snapshots__/FilterDropdown-test.tsx.snap
@@ -7,8 +7,8 @@ exports[`<FilterDropdown /> renders dropdown options in menu 1`] = `
   role="listbox"
 >
   <div
-    aria-selected="false"
-    class="mx_Dropdown_option"
+    aria-selected="true"
+    class="mx_Dropdown_option mx_Dropdown_option_highlight"
     id="test__one"
     role="option"
   >