@wicknix - things aren't going quite well with 27.10.1a, and apparently it's not only YouTube-related. I've noticed that if I open a number of tabs at the same time (say, a series of links inside an article), AF now goes on “panting” while opening them. This had never been the case. With my limited understanding taking a closer look, it seems that it churns to translate what it's getting before suddenly rendering the page. Or only part of it, occasionally. Maybe it's the images, or embedded videos, that are slowing things down.
It wouldn't be too much of a problem (I can't read several tabs simultaneously anyway) if AF wasn't crashing much more often than it used to. 27.9.18 never crashed more than every couple of months or so. Matter of fact, the last monthly DiagnosticReports I have kept only show two crashes in January, whereas now in February I'm already up to 10 of them (including the couple of YouTube-related ones mentioned earlier). If you wish I'll mail those logs to you.
The last recorded crashes happened yesterday, after I'd noticed that instead of AF's normal tiny CPU usage (1-5%) with peaks of 100% and slightly over when it's busy, it was constantly hovering around 300% with peaks of up to 400%. After closing all active tabs (not pin tabs), CPU% didn't change, and when I quit AF it crashed. Relaunched it (essentially to make sure the profile was not corrupted, my biggest concern), didn't do much with it, but when I closed it down half-an-hour later, it crashed again.
Note that this abnormal CPU usage appears to be rather stable, doesn't resemble what I remember from every 3 or 4 versions of Firefox, when memory usage went slowly building up (memory leak?)
To add to the (your) fun, I even had AF
freeze on me two days ago… and
freezing the machine with it too ! Time warp, like being thrown back to the days of OS9. No log of course, but the hassle of having to verify disk etc.
Not putting any demands on you of course, but if you have a vague idea of a timeline, I'll figure whether to temporarily go back to using 9.18 or not.
But whatever you do, please don't do what the Pale Moon people have pulled out on us with their last update (my first one in the system I'd installed it on): without asking it disabled over half of the addons, including even the current Theme. By the time I'd painstakingly enabled them again, all their settings as well as the interface setup had left to some other plane. A real disgrace, lucky I had a backup.