Discussion about the Korg PolySix synthesizer

As far as I know the memory chip will not result in such a behaviour. In
fact, the CPU board will work fine without the memory chip (of course
without the ability to store sounds).

Continuity is a good thing but it doesn't reveal if there are additional
shorts between traces.

Both the VCO octave switch and the sub octave switch use the same lines:
P10 and P11.
You might want to check the following functions:

EG Switch
Effects switch
Attenuator

I'm quite certain that either the P10 or P11 connection is broken somewhere
(or possibly both, I will have to check the PCB layout for this.)