I took my iPhone 6 to my local Apple store today because the lower right corner was 'clicking' and a touch loose as it had been since I got it. In truth it didn't overly bother me but I was concerned dust or moisture might get in. Anyway, straight away the genius knew the problem and arranged for the screen to be replaced (90 mins) I asked if it was a common problem and he said it was a decent percentage, higher than most issues. As I said the speed he recognised it and his comments suggest it's definitely an issue the stores are more than familiar with it. wether or not Apple themselves are aware of it or not, who knows. Thought I'd share this incase anyone else was having a similar problem.