Vintage Synth Repair

I have a related problem:

It seems that the ADSR amount going into the VCA on my white-face Ody
starts to "creep" up as it warms up, so that, after an hour or so of
playing, there is a constant drone, even though the VCA Gain is down
and no note is being played.  The amount of Release on the ADSR
doesn't make any difference.

I have to either pull the EG Amount slider down to about half or
switch out the ADSR and use the AR envelope generator on the VCA.

Anybody ever run into that?