aha yes this makes sense! thankyou! there were some tiny bits of debris in the unit while i was working on it but i didn't have compressed air so couldn't clean it. and it did indeed start working randomly after i moved it around some. i will give it a good clean when i fit new sequencer buttons.
this synth is almost as old as me. needed a bit of love and solder and a lot of delicate button cleaning to get working. just checking it out. first a preset...