Hello, I bought a second-hand iPhone 5S which has no scratches or dead pixels on the screen. However, sometimes, some portion of the screen becomes unresponsive while it seems to throw random touches. After a restart or perhaps just waiting for some time, it comes back to normal functioning. I've tried updating iOS (from 10 to 11, including the latest 10.0.3 which promises to solve touchscreen problems), but this random behavior continues appearing from time to time. Any ideas on how to solve the issue? TouchID works flawlessly and, as I previously said, the screen has no scratches or shows any signs of dead/hot pixels.