I've owned my iPhone 6 for 54 days to be exact and from around the first week or so I accidentally tapped on the right side bottom corner and I heard a click and didn't think anything of it well a few days later it did it again and I begin to read online and I see quite a few other people have it. Well after a bit of time of it seeming to click once or twice a week I made an appointment at my local Apple Store. When I sat down at the Genius Bar I told the guy my issue and he said yeah that happened to mine as well ! Well they tried pushing it and it didn't click and said of you can't replicate the sound we can't help you and I had to leave , should apple have done more or am I just crazy ?