Screen sometimes blends out (getting darker)

I recently bought a 47pfl6877k/12. I only use the TV with my HD sattelite receiver so no antenna cable connected to the TV.
I upgrade the software to QF1EU-0.150.48.13.

My problem is that when I use the menu of my satellitereceiver sometimes the screen is getting darker and the menu options are difficult to see. It is not at all menu items: some are good, some are getting too dark.

I switched in configuration the light sensor off but unfortunately.

Of course I tested it at another TV to be sure that it has nothing to do with my receiver. At other TV's everything is working ok, so it must be a setting in my 47pfl... TV or a software bug.

Question is: how to switch it off so that the brightness of my TV screen will not be changed when using menu items from my satellitereceiver. Any help will be appreciated.

Later:
for some reason I can not update the firmware with the online software update feature (no new releases found). So unfortunately I had to update the firmware by using a USB stick. I now have I updated the firmware by using an USB Stick so my current firwmare is now QF1EU-0.150.82.0. Problem with darker screen is not solved so it still exists

Try to switch off (or set at MIN) the picture "improvements" like light sensor, dynamic backlight, perfect contrast, etc. and try again.

@Cookie: tnx for replying. I can of course switch off a lot regarding picture but then I will have a black screen....lol
So switching off things like dynamic backlight, perfect contrast, etc. is not the solution. I think there must be one setting which will prevent my screen from getting darker. While other things like a sensor for ambilight led's should continue to work properly or... So question still is: how to prevent my screen from getting autom. dark while ambilight feature reacts properly at light-changes.