For the last 2 or 3 weeks, I have a problem related to html5 where it will suddenly stop working: no image, no sound, nothing. It can happens in the middle of a video or stream, and when it happens, it stops working on every websites (youtube, twitch, etc) until I restart firefox. It's also totally random, can happen when FF was last restarted few hours ago, or days ago. I've tried clearing the cache but it doesn't change anything. When forcing some sites to use flash instead, it works... but when I force them to html5 again, it is still not working. I'm using the same addons for months, if not years, and never had this problem until recently. I even totally reinstalled FF yesterday, deleting all files everywhere before just in case.

any idea?