White bar on top of window going onto another monitor
I've recently had an issue where there is a white bar on one of my other monitors when Firefox is maximised. I have reinstalled Firefox, restarted in Safe Mode, uninstalled it completely and tried a different build (I tried Nightly 80.0a1) and it has remained the same.
The issue does not occur on any other window or browser; I have tried Edge and Chrome and it doesn't occur on either of those.
Here is how it looks in a screenshot (note the white line between the top of the Firefox window and my wallpaper)