Currently, I am slowly moving through each of my song, and fixing their tags. I have two monitors in a vertical configuration, Chrome on the bottom and Mp3Tag on the top. I've noticed that sometimes if I whip my cursor down to the bottom screen, another file will arbitrarily be selected in Mp3Tag. This sometimes causes me to accidentally apply tags to multiple songs at once, when I really only meant to apply them to the first song I selected, because for some reason another song got selected. This is pretty bizarre, but nevertheless it's happening. I used to notice it happen with one display as well, when I had Chrome and Mp3Tag split horizontally on the display, but at some point it stopped happening, and I thought that was that, but apparently not.
Anywho, I'm on Windows 10 20H2 (19042.868) and Mp3Tag v3.05.