Hey there! It sounds like you're facing a bit of trouble with videos on YouTube after the recent Firefox update. Don't worry, you're not alone in this. Sometimes, updates can lead to minor glitches like the one you're experiencing. To fix this, try clearing your browser's cache and cookies first. If that doesn't do the trick, you might want to disable any extensions you're using and restart Firefox. If the issue persists, you could also try updating your graphics drivers, as they sometimes play a role in video playback. Give these steps a shot, and hopefully, your YouTube videos will be back to playing perfectly in sync.