Stefan Mileschin

If you thought you were the only one with a screwed up iPhone 5S, don't worry, you are not alone. Nobody knows what is wrong yet, but at least this prevents you from returning your phone over and over thinking you'll get one that isn't broke. The problem seems to be incredibly widespread, but it also affects different phones in different ways. If it were consistent across the board—for example if the compass was 2-degrees off for everyone—then it would be easier to pin the blame on iOS 7. The solution to the current sensor woes, then, could be as simple as a firmware fix to make the calibration more accurate.

http://www.hardocp.com/news/2013/10/...ly_screwed_up/