A strange thing is happening on my two laptops both running Firefox 50.0.2 and Windows 10. I have two separate Firefox windows open and use the snap feature to split the two on the screen. Then I decide to maximize one Firefox window while the 2nd sits behind the maximized window. Randomly the 2nd window just pops up on the screen in the same split position that I left it before in front of the maximized window. I focus back on the maximized window, and a few minutes later it pops up again. Sometimes this happens again if I click on the start menu. This is really annoying when I am trying to work on something in full screen mode. This doesn't happen if I minimize the 2nd window before maximizing the 1st, but I never had to do this in the past with W7. I tried disabling snap assist but can't seem to find any other troubleshooting from searching. This only seems to happen with Firefox thus far in Win10. I could not replicate it with other applications.