Ghost touches, a dead zone, or you have to press hard.
A screen damaged by a drop or liquid, or a badly fitted protector.
We test without the protector and with a known-good screen; if it's the screen, we replace it.
It depends on the model and on what we find inside, so we quote each repair individually. The diagnosis fee depends on the device, and you approve the exact repair price before any repair starts. If it can't be fixed, you only pay the diagnosis.