If you set the default dark blue water background for the lock screen, turn up the brightness a bit, lock the phone, and swipe from left to right above the slide to unlock thing, using just a tiny bit of pressure, does your screen have these wave like things? It looks like screen is not seated properly or something. This happens anywhere on the screen really, if I use just a little force. When I say force, I mean just a little more force than you would use when you tap the screen. The waves look like these colorful bands like if you press too hard on the screen, but I am not pressing hard at all.