I had the same problem but fixed it. My problem was that the camera was getting in the way. It actually required me to remove the motherboard to access the camera though.
The camera has three parts: actual camera, a metal cover, and the aluminium(?) sheet merged together with the plastic backing protecting the motherboard. In my case, I got the phone second hand and they had tried to fix the camera and put it together wrong. The problem was that they put the metal cover in the wrong place.
1. The metal cover has a corner that is 'cut off'. This goes in the upper right when you look down at your phone.
2. The metal cover also has a part that sticks out. It looks like it's actually supposed to go underneath the motherboard, but the videos I saw shows that this sticking out part goes on top of the motherboard. Also it's the only way to get the back to click into place.
This might not be your problem, but good luck with it!
