The strangest thing has happened. I've repaired 3 Phones recently (z5 compact, Lumia 830 and Nexus 6P)
The proximity sensor on all 3 phones has failed after screen change.
I'm hoping the problem is the same for all 3 and all I can think of is that perhaps I've over heated the sensor during screen removal(?)
Anyone can shed light on this would be great thanks.