Hi, I posted this question about 3 upgrades ago. I run Win7_64 (Yes I know it's outdated!) with dual monitors. After closing FF I was always left with a partial FF screen window open on the left monitor. It could only be cleared with a screen refresh, or dragging another app. screen over the top. I checked the obvious like GFX drivers (which had never changed), FF .exe processes seem to have terminated and I confirmed no other app did this (even Chrome). I suspected it was a FF shutdown problem? I asked the question here but didn't get a solution until now.

I've now installed the latest update 115.11.Oesr (64 bit) and have not seen the same problem for a week. If it stays that way, thanks to the FF team for fixing this annoying problem.