I am guessing that it is just an issue with the screen. It would most likely be fixed if you replaced it. Has the phone been water damaged at all? That is the only other thing I can think of that might mess up the screen without it being broken. If you are thinking of doing the repair by your self, make sure you test the new screen before you actually install it all the way to make sure that the issue was with the old screen and not a more internal issue. Good luck! :)