[projectRDM]

Is the plastic insulator on the charging stud cracked or damaged? That would be the first thing to check, if it's fine then he did some kind of damage when polishing it. It's not overcharging though, that would mean the voltage regulator is bad and you'd see increased voltage, not amperage. Something is grounding out, maybe a winding got some grit on it and when it expands from the heat it's touching the case or something similar.