3 ground contacts bridged, no difference.
Probably like Roland Cube pot problems. All pots except the master , are
used as digital controls, 0 and 3.3V dc on the ends. Amazingly only one
of the 7 "digital" pots you can turn down to a few ohms , all others
many DVM-R ,Ks to megs and wavering. As there is polling signals on the
front panel switches the main uC must be ok , for that anyway, and I
assume there must be a control logic that locks out the whole system if
the ADC voltages are wavering about , beyond some set minimum for the
user doing an adjustment of one perhaps at a time