There is a ~3px space above tabs on the title bar when I run Firefox maximized (not full screen mode) on my external monitors, meaning if I click at the topmost part of the screen above a tab, the tab is not selected. If I double-click instead, the Firefox window resizes out of maximized view, which indicates the window is indeed maximized and there is not a display problem. This does not happen on my primary laptop monitor, which is a 2880x1800 display scaled to 150%. The external monitors are both 1920x1080 with 100% scaling; if I change the scaling on the external monitors to 150% to match the primary, the problem goes away. If i change the scaling on the primary monitor to 100% to match the external monitors, the problem remains. Any suggestions?