I'm out of ideas on how to fix this, every now and then my Firefox browser gets a random white border around it. Windows 11, no compatibility mode active for the application.
When I maximize and minimize the window it goes away for a while.
One possible hint: This has started to show up after adding a third display (a 4K TV) to my setup. Even if the TV is fully off. But the TV is the only display which has a different resolution scaling active (all other displays are at 100%).
surprised windows 11 is even capable of rendering borders, but yeah that's pretty much what's happening here, looks similar to on 10 when using a theme with borders. I guess whatever is done to hide the borders when maximizing still works, but it showing the borders while not maximized somehow happens despite the theme not being built for it (maybe an issue with DWM?)