It's happening more and more frequently that once I go to a YouTube video page, I get the error "An error occurred. Please try again later.". When the issue happens, it's reproducible with all YouTube videos. Switching to Chromium fixes the problem. Although MPV with youtube-dl integration works even better.
Ask HN: Has anybody else had issues playing YouTube videos in Firefox? | Better HN
The only minor annoyance I have is that I put a video on fullscreen, it takes a second or so. First the frame resizes and then the picture, doesn't happen with chromium/chrome.