Hi Tom,
I had a similar issue with one board on my CS60.
The problem was the following: the envelope of the VCF had a two states behavior, that is it jumped immediately from start level to sustain level when a key was pressed, then immediately back to start level at the release of the key. This was obvious using a panel settings with the EG-VCF sliders all the way up. Changing IC1 solved this issue.
Joachim
I had a similar issue with one board on my CS60.
The problem was the following: the envelope of the VCF had a two states behavior, that is it jumped immediately from start level to sustain level when a key was pressed, then immediately back to start level at the release of the key. This was obvious using a panel settings with the EG-VCF sliders all the way up. Changing IC1 solved this issue.
Joachim