I also have this issue. In my case I'm watching fullscreen TV with EON app when someone calls me. This is very annoying - after the call, the auto brightness stops working until the next reboot. Even more, while the issue is triggered, the proximity sensor during calls starts to react with large delays - when I remove the phone from the ear, the screen may not turn on for long time. In most cases I have to press several times the power button to turn the screen on.
While auto brightness is not working, the Light sensor SMMI test shows ADC=0 constantly.
