LG G2 proximity sensor I found a big issue in my LG G2 proximity sensor. During a phone call the screen doesn't turn off and the automatic screen lightness doesn't work. This problems happened many times a day. I also tried to do an hard reset but I got the same issue just after the reset reboot (without any app). Sometimes also the gravity sensor holds (screen doesn't turn), but this not so often as proximity sensor problem.
I installed a sensor test app and this app doesn't work too (sometimes got data sometimes not).

What can it be?

Firstly I thought about an software problem, after the hard reset I thought an hardware problem, but it is very strange all this trouble on a 2month old phone. These problems started 2 weeks ago.

Is there in android a system log or something like this?
Had similar issue with G2 after display replacement. Unfortunately this could be solved only by replacing the proximity sensor itself (via warranty repair). From the information I found out on the web 

The most disturbing issue was that I could not unlock the phone in dark light environment (the screen immediately turned off when I tried to go past the lockscreen).