FP6 brightness randomly gets scaled down

I was redirected here after my post:

It has nothing to do with the screen timeout. The screen is far too dimmed just when I switch it on and will not get brighter in 10 ore more seconds.

And it looks like the sensor cannot divide “almost dark” from “absolute dark”. The lowest dim level is set far too soon.

I have an anti-glare screen protector which makes it more bad, I think. But I do not want to miss the anti-glare in most light conditions.

Do the FP6 use the front cam for brightness detection?