The ground connection to the regulator on the SS is poor, tightened as it is against the rubber wellnut (photo above) It really needs a nut at the back, between reg body and the wellnut to get a good, tight electrical bond. Complicates the mounting but worth it.
Yes it’s a bit of a crappy earth on the early models with the well nut reg/rectifier mounting, the later from 95 ish had captive nuts so you get a proper earth…
As above, In the Haynes manual it mentions about this. " Ducati recommend that the rubber washers fitted to early models be replaced with the steel washers fitted to later models as they improve the heat transfer of the unit"