This morning I woke up to find the gap between the two halves of the phone slightly (noticeably) wider than normal. I slid it open to find that the bezel around the screen's back mirror was loose and had popped off by about 1.5mm. I pressed it back into place and it clicked in, so all's fine now.
Question is, is this because i've been sliding the screen up by pushing on the very bottom, slowly forcing the bezel to pop off? Only mildly worrying, but thought i'd share.