One quick check would be to confirm the Cutout Relay contacts in the VR are not "welded" together from pitting. If they stick together, current can go backward from the battery to the starter generator EVEN WITH THE KEY IN THE OFF POSITION.
Open the VR
Locate the Cutout relay. The wire windings on the Cutout relay will be a much larger diameter than the volt / current relay
Press down on the relay contact arm (marked with the "X") and observe the contacts - they should open up completely - probably around matchbook cover thickness.
If the contacts fail to open or "pop" open, there may be significant pitting bridging the gap.
Cleaning the relay contacts with a points file can temporarily restore proper operation to the VR.
400 grit wet / dry paper on the contacts can also be used as a temporary fix.