To restore animated thumbnail previews. Requires inline video previews to be disabled in your YouTube user settings (Go to https://www.youtube.com/account_playback and set "video previews" to disabled). Not Greasemonkey compatible. v5 Add new method for getting an_webp GIF-style thumbs when not available in YT's new homepage UI or subscription page UI.
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Good spot thanks! Fixed in v5.9.
Works fine but the interval won't stop due to clearTimeout instead of clearInterval