Mark Levinson 39 Drawer problem

I have a problem with my ML 39: It seems that the drawer is not communicating with the main unit. The loading drawer does not open or close, the display states "Drawer" or "opening" or "closing" before "Stopped!"
I checked the internal connections between drawer and main board and also looked for obvious issues on the drawer unit.
I do not have a service manual...

Thanks for all feedback