I must have rearranged the screws after replacing the battery in my iPhone 5 because my compass stopped working. I went back into the phone after reading this post and I put the screws in their correct locations. Well, at least I though that I had. I also found out that a magnet attracted all of the screws so I used a magnetizer/demagnetizer (purchased at a hardware store) to demagnetize the screw at the top right. This solved the problem for a little while but the problem has now come back and the compass will not calibrate. I'll go back in and loosen the screw to see what that does. I'll post an update.