Does it happen after opening certain applications? I know AR apps aren't pretty right now, I can crash (Spinning wheel as well as lockup) the X by opening at least 2 of the top AR apps in the app store right now. I've stayed clear of them because of this. And this does occur on IOS 11.1 and the latest beta 11.2. I've submitted my testing to Apple as well as the developers of the apps I've seen cause this issue. Also it can be caused by older applications that aren't updated yet, not necessarily just AR apps.