Same here as well- I exchanged my first iphone 5S a couple weeks ago under warranty for a defect in the oleophobic coating (had this weird smudge that you clean off, but once you started using the phone it would return.. and was visable against light backgrounds). Now this one has the 'double click' sound, if I'm push down the home button for a few a seconds it'll go away for a while- I'm guessing part of the adhesive isn't holding properly. I'll probably hold off on try to exchange it again- this one does much better with it's touchid sensor. The first one would give me a 'try again' 50% of the time for any of the fingers I programmed it for, even after relearning. The new I haven't received a single false negative yet.