Lightning contact malfunction

My iPhone 5, just 1 year old is getting harder and harder to charge. The charger has to be connected from an exact right angle to charge. The exact same thing happened to my iPhone 4 and my 3GS as well, where the problem were the dock contact which I've changed in the earlier models. I really don't understand how it's possible that this happens again. Anyone else who has had the similar (reccuring) problem?