Problem: when I make new firefox window(launch .exe, drag a tab out, shift+left click link...), there is tiny gap between screen edge and new firefox window. (fullscreen works ok) Expected behavior: no gap between screen border and new firefox window Image 1: firefox window snapped to right. Image 2: new firefox window after minimize right-snapped window. Image 3: firefox window across left screen border. Image 4: new firefox window after minimize across-left-border window. Tried: edit&delete xulstore.json, reset firefox, uninstall and reinstall firefox. still same issue