just did our 31A paint stripper and lot of scraping got big amount off. took to get it blasted guy used crushed glass, did not heat up metal like sand can. had him do inside and door jambs took out old body filler which we wanted. going to do a restore I suggest using doing this.
I agree usually is a bad ground causes this ,trace all wires wherever you have a wire going to ground sand down and use some vaseline before hooking back together,also put this on contacts of bulb and around base of bulb for easier removal later.