3 days ago my knock on feature stopped working and have noticed what might be dead spots in the screen first playing angry birds. I tested again using the notebook app and there are dead spots, but in some cases it seems to be pressure related and need to press very hard to dry lines in the bad spot at the top of the screen. I have done checked / unchecked knock on gestures and performed a full factory reset and the problem persists. I tried to file a claim via the Asurion website, but said that the issue was not covered.