Yamaha CS80

Hi, group,

My beautiful CS-80 has a minor issue: One of the upper-row voices seems to only have the sine wave suboscillator, but no VCO-VCF in it. This is obviously more noticeable if I silence the bottom row, and if I mix both rows equally it becomes barely perceptible, kinda' like a muffled note caused by hitting the key too slowly.
It is a barely-noticeable "blemish", but I hate it.

Anybody want to tackle this one?
I have tried contacting Old Crow using the email from his CS80 site, but it bounces back.

Hope you guys can come up with a solution.

Thanks!!!

JDiaz