I have this problem as well. The joke is, my iPhone 6 was an original run purchased that September. The crescent shift did not materialize, what happened instead was tiny specks of dust appeared between the camera lens and the glass. I ignored it for a while and then happened to ask about it while i was in the Apple store. The concierge told me that it should be fixed and she made a genius appointment for me on the spot. The tech checked it out and said they would replace the display. When we told me how long it would take, i balked a bit since i was paying for parking by the hour. When i i hesitated, he said, "you know what, i know you're a good customer, so i'll just replace that for you right now."
So that was very nice of him. And then my replacement phone almost immediately 'crescented' 😡 It's getting worse, too. It is almost 1/3 of the way over now.