7 plus 128gb. iOS 10.0.2. I had this same issue on another 7plus 128gb. Sometimes the phone will randomly go to a black loading screen (where the little thing in the middle spins) for about 2 seconds and then return to the lock screen prompting me to use Touch ID or enter my passcode. It mainly happens after taking a picture on 2x. Also, sometimes when I open the camera app, the scene will be frozen until I close out of it, end the process, and reopen.