Same problem - more or less. I'm a fan of Reddit and whenever I now come across a YouTube video clip I know it's a waste of time clicking on the link. If I do so, it'll load for some 20 seconds or so and then come up with an error message: "An Error Occurred. Please Try Again Later." The Playback ID is also displayed. I know damn well that it's a waste of time to 'try later' so all I can do is to head over to YouTube, search for the video and then play it there. It's a Firefox problem that used to happen soon after tthe last version of Firefox came out - and then it was sorted out - but now it's back. Yet another reason why I'm getting thoroughly fed up with Firefox.

My solution is to open any youtube videos in an alternate browser to Firefox... but this is just a pain... And forms Twitter sends to threat you over your account, also do not work in firefox. And Gab.com does not work in firefox...

Though i have used firefox for 15 years or more, maybe its time to start looking for a new browser...