Ok folks: I fixed my Monopoly, no more VCA bleed!

Thanks to
@SkyWriter and @
jags for posting info and pictures that helped me a lot.
Getting to the pcb is as easy as removing 29 knobs and 37 screws; then unplug 3 connectors and cut the tie that holds the keyboard cable to the pcb, solder a jumper wire from pin 5 of IC8 to the lower right pin of VR10 (CCW when viewed from underside) and put back all the stuff together.
backplate removed, the left pcb is held by 12 screws
keyboard connector
VCF-VCA-EG pcb, IC8 is top right
detail of VR10 - IC8
spotted a bad solder on VR10 pins, apparently it doesn't make harm but I resoldered it
the jumper wire
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Then I focused on Pitch Bend and Modulation wheels. I always had the impression they looked cheap and flimsy compared to other synthesizers I owned, spring action is too strong to my taste, and I can't stand the squeaky noise they produce under the lightest pressure.
4 screws on the underside release the wheels sub-chassis (made in solid steel)
unscrew the wheels plastic frame from the metal chassis
wheels
unscrew pot pcb to release the pitchbend wheel
remove the spring and separate the plastic sides
fill the space inside the wheel with sealant
glue a neodymium magnet to create a (hopefully) self-centering action
fill the modulation wheel with sealant
a second neodymium magnet placed under the pitch bend wheel should help to keep it on zero position, apply bending with zero force and park the wheel where I need it to be.
Now I can use the bend wheel to steadily detune VCOs by max. +/- 29 semitones for infra/ultrasonic patches, in addition the wheels feel more solid than before.