I got a new nokia830 with 8.1. When I make a call the screen goes dark right away. It's a problem if I need to enter digits on a automated answer. I can hit the power button a few times and may get screen back but sometimes it hangs up because I hit too many times. I read some other instances of this and remedies were to blow into ear jack or remove screen protector. Neither worked. I took it to point of purchase and they have no idea as they hardly sell the phone. I took it to best buy geek squad and then it was ok. I went home and not working again. I wonder if led lighting at best buy alters the sensor. Has anyone experienced this?