Korg MS-10 oscillator bleed/noisy square wave questions

I am in the process of fixing up an ms-10 that has the following issues:

-the oscillator is still fairly audible even when the filter is all the way down

-the square wave is somewhat noisy while the other two waves are not.

I thought I would just go through and replace most of the capacitors, but that seems kind of a over-reaching solution if I don't know the source of the problem to start with.  

Does anyone have any suggestions as to where these problems might be originating from?

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