shalokshalom 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 layers.acceleration.force-enabled to true. This fixes the issue for me and here is the issue on Mozilla`s Bugtracker.
demm 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?