Since 19 days, Firefox drives crazy on my machine.
I suspect the new mesa is the issue. You can fix this via about:config and setting
to true. This fixes the issue for me and here is the issue on Mozilla`s Bugtracker.
Mesa 19.1 is in the build repo, will move shortly, please report back if that fixes any. Also, still an issue with Firefox 68?
Yes, still an issue on 68 and I report back, once 19.1 is in main, thanks.