Xpantastic!

Hi everybody,
Can anyone help me ? I've got this voice problem with my Xpander:
on voices 2 and 3, the 2nd VCO doesn't work, and it's NOT the 3374
nor the filters. I've changed them all. I'm starting to think that it
must be some digital control over the analog voices that is failing.
Is there someone who has had this kind of problem? I'll be grateful
for any suggestion.
Thanks to everybody,
Philippe