I've been having an issue with having my firefox window being maximized on my bottom screen and a portion of the window being displayed on the top screen. It's a weird issue, but when I try any other browser maximized, this doesn't happen. I included a screen snip of what is being displayed on my screens. You will see my tabs, and right above, you will see the sliver of window that shouldn't be displayed along with my wallpaper. Sometimes this sliver of window looks different, displaying the top half of my tabs, other times it's completely white or black.