Hello, I find that Firefox has flickering lines across the menu bar in full screen as well as in smaller format but only if the menu bar is in the top 1/4 of the screen. This behavior also appears with a printscreen of Firefox pasted in MS Word but only if zoomed in a fair bit, the lines, even in the printscreen situation, flicker, but only in the menu portion of Firefox. This does not happen with other programs and doesn't change if I restart with the add-ons disabled. The printscreen behavior really has me puzzled. I can hide the menu and all is working normally, I do like to have the menu present to work though. This is happening on a Windows 10 Home edition machine on an external monitor connected via HDMI with Firefox 50.1.0. Any window that is put in the path of the flickering lines will get them until you go up far enough to maximize the window. Also, a new private window will do the same almost, it will get the lines on the tab as well as the menu.