Discussion about the Korg PolySix synthesizer

hi all, i am having a bizarre issue on one voice of my P6, hoping you all may have an idea.

the envelope seems to be starting at an "off" place on voice #3. by playing with the timing or attack/decay settings, it seems that they all TIME the same, its just that one voice sounds noticeably different when the EG is controlling the filter. with the EG off, i can get the bad voice to sound identical to the rest, so it seems to me its not a filter calibration. i tried switching the SSM filter chip, and the problem did NOT commute with the chip. looking at the board, i'd probably just be shotgunning the elec cap and the 4558, but that's just me guessing.

any more informed ideas than my guess? thanks, rj