Okay, so I've repaired many iPhone 4 screens since i started in this business. About 3 times this issue has occurred. I swap the screen out as usually, then when I turn it on the Camera crashes. Sometimes the back cam works but then I switch it to the back and it crashes! I have tried everything from switching the cams to restoring the phone . Nothing works! The lens just stays closed and flickers at the bottom. Anyone know how this problem happens? How to fix it? Or how to avoid it !