So does a reboot or restore fix this? I assume something "fixes" it since you mentioned this happens on two different versions of iOS. My feeling is it isn't a connection issue if a simple reboot/restore fixes it.
Nope. Reboot or restore doesn't fix anything. I'm back to iOS 6 and it just happened when I woke up.
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More than likely a hardware issue. It could be a bad connector, or even a faulty GPU which would require a full logic board replacement (if not a full phone swap-out). In any case, if a restore doesn't fix it, then it's time to make a trip to he Apple Store.
Looks like Apple store will do..
But the service here in Korea is crap though. For some weird reason, I've had five faulty iPhones 5 so far, and none seems to be perfect. I got the
phones replaced for battery, battery, camera, dead pixel issues. This fifth one is just going crazy with the display....