After leaving the synth on for a while I couldn't even get Chord Mem or Hold buttons to react. After cycling the power they reacted again but had hanging notes.. I was then pressing all the key assign buttons and after some clicks it started behaving properly... Now all those dead notes are playing fine (except the last G, A & A# are still very dead).. Very odd. I wouldn't be surprised if it happens again. I'm still unsure where a fault like that would be found in the circuit.
Well- I still have to install about 3 new button cap holders and clean the volume pot, so I would be surprised if the issue arises again, if it does I'll make sure to update this thread.