Well, the soundcheck of my Satin today proved that with fingers lifted from the strings, the guitar hums appreciably. Gotta be a wiring ground issue. With finger on the strings, little to no hum. Off to the new luthier next week to check for wiring and/or spray shielding.
I think the ground wire goes from the cavity to the bridge. Feed the wire in through the hole until it touches the bridge. (Buzz stops) then hold the wire in, finger tighten a screw into that hole, just a tiny screw, enough to hold on cavity cover - it should hold that there in place, save you money and a trip to a luthier.