Vintage Synth Repair

Hey folks,

I have a nice little Micropreset that is getting fussy.

Here are the general symptoms:

On certain "patches", everything is fine. On others, some stops are missing, and the two "Synthe" buttons don't work at all. 


Here are the details:

Voice - All good. 
Wood - only 8 and 32 work.
String - all good.
Brass - all good.
Synthe 1 - none work.
Synthe 2 - none work.

I recently took it to a tech who decided that he wanted nothing to do with it, so I'm now on my own. I have a bit of electrical knowledge and soldering skill, so maybe with some help I can fix this neat old instrument.

Thanks everyone!