I just wanted to give a quick thanks to the OP of this thread.
I just did a mass purchase of screens from HK to fix 4 phones.
3 Nexus 4's and 1 Optimus G lcd / digitizer / frames replaced and the proximity sensor would not work on any of them. After much assembly and disassemble I found this thread.
The quick fix of turning the rubber gasket to the wrong holes on the sensor fixed them all! I dont know why it works, but it does work!
They all now work perfectly.
I used: Proximity Sensor Finder
for troubleshooting while trying to find a fix and verify the fix.