Full screen shows bands on top and left, first time, but doesn't do it in private window or second time
When I first use full-screen mode with Firefox, small bands appear on the top and left sides of the full-screen window. The second time I use it, it appears normally.
I have tried a fresh profile, it doesn't happen in a fresh profile. I have tried in safe-mode, doesn't happen in safe-mode. I have tried turning off all extensions, it still happens.
When I run in a private window, it doesn't happen either.
Any idea what's happening in safe-mode and a private window that fixes the problem.
It's really just an annoyance, but I'd like to nail this bizarre behavior down and fix it.
Any ideas? Thanks.