Yamaha CS80

Hi all, 
after about 8 months (8!)  I am going to complete the overhauling / calibration of my CS80.
The only problem I have now is that in one voice the EG Filter envelope, at both the calibration voltages/speeds (8 and 3V) , as shown by the scope, is about 1V higher than in the other voices, neither am I able to lower it in any way. I tried to workaround replacing the ICs (both the VCFEG and its VCA) and other components, but nothing.
The result is a "more open" filter only in that voice. 
I am sure that there is somebody who faced such a problem!
Waiting for help 
Thanks

Fernando