Thank you. I sorted the problem. The dealer installed an in-between converter cable, to fit the system to the car electronics. Apparantly they were aware that they had to cross colours (I mean, yellow to red and red to yellow) in order to have constant power in the right place. But, they accidentily crossed it at the input of the converter and again at the output side. That way, cancelling out the first crossing of the wire. I undid it at one end, and now audio settings are remembered. problem fixed.
Still curious how this effects only part of the settings. Apparantly different settings are s