I have a weird problem with Firefox 48.0.2 on my Surface Pro 4. When I go into Tablet Mode, Firefox doesn't go full screen. I've played around with it, and it seems to go to whatever size the window was when "restore down" mode was in desktop mode. I don't know if that made sense. So, if I open Firefox in desktop mode, it'll go full screen fine. I'll enable "restore down" mode by clicking on the little square icon by the "close" x, - the window will then be re-sizable. Then, I can go back to full screen. If I then close Firefox, and open it when in Tablet Mode, it will open in whatever size the window was when it was in that resizable mode earlier, only I can't resize it or maximize it, of course, because it's now in Tablet Mode. I can't figure out what's going on. I tried deleting that xulstore.json file, to no effect. Any suggestions? Thanks!