After a few times trying it finally accepted the command for 'mode 1' and the result is that sometimes part of the local keyboard works...
But the strange events are still there: sometimes it doesn't 'see' the remote, if i turn the wheel of the doors a bit so the switch is in 'no contact' than it works again.
But this is not always, sometimes it just keeps on 'seeing' the remote and doors work normal.
Also (if it works) pressing [tape] results in the tapedeck starting to playback, with no tape in it !
Sometimes it goes 'normal' into standby (doors close, lights off) but sometimes the lights stay on....
So it's a bit like a haunted beosystem....
I had already cleaned and measured the switches of the door and cd clamo (open/close detect) since they're connected to the keyboard multiplexer, but no result.
It still leaves me with a suspicion about the cpu.
Now i can borrow an Ouverture here to try and swap the cpu but (so far) no 2500, would that work ?