Whenever I put a Firefox window on my second monitor or split the monitor with a Firefox window and something else, Firefox is always a couple pixels wider. Whenever I click the window to focus, it shows the extra pixels and it overlaps either on the window next to it or from the second monitor to the first. It's a very minor issue but it's so annoying because literally no other program that I have ever used does this. I've included screenshots of my main monitor while I'm focused on the window on my second monitor. I've included two screenshots where the window is snapped to the top half and bottom half (the second monitor is vertical).