Discussion about the Korg PolySix synthesizer

I bought a Poly six on E-bay.  Of course it has some problems.  I did 
the "OldCrow" battery mod and trace repair to resolve any problems 
associated with battery leakage.  

But Now I still have some issues:

 There is a problem when the resonance is up high and the eg reduced, 
five of the six voices are quiet and the sixth is very loud. Also some 
distortion is heard on some voices but not others when the resonance 
is cranked. 

This weekend I tuned all the voices to each other. The high range now 
plays in tune relative to itself.  The low range has a progressive 
drop off in pitch, the farther down the board you go the more it goes 
flat.

Also when holding a key down the tone will go into oscillation 
intermittently, and especially before the unit warms up.  A patch with 
no modulation will suddenly start warbling if you hold a key for a few 
seconds.   

Anybody with any ideas?