Summer is back in germany, so I happily pressed the "back" button of my sunroof, but it did not move.
so I pressed the "forward" button and it moved to the vent up position.

As my back button still didn't work, I pressed the forward button again.
It moved a bit forward before it moved like I was pressing the "back" button.

It seems that I can steer all functions of my sunroof just with the "forward" button.

Is this a software fault ?

How can I find out, what is causing my "back" button to fail ?

 

I found the reason for this:
Pressing the forward button a certain time, you end up in sunroof-calibration-mode.
I had to end the calibration to bring back normal operation.