Discussion about the Korg PolySix synthesizer

hi, 
i am working on a polysix that is sometimes perfectly functional for long stretches, but 
randomly exhibits a weird problem. it seems to have nothing to do with how long it's been 
on. basically, the bank d button and patch 4 button start to come on and the patch starts 
to deteriorate, turning on vco modulation, pwm, etc, and doesn't want to save patterns 
correctly. it's always d and 4. the battery has recently been replaced with a new one, and 
some minor corrosion damaged was repaired. sometimes the synth behaves normally, and 
has no problem saving and recalling patches. 
any ideas? 
thanks, 
greg