Lost one of your lug screws or even one of the screws for the plastic cover? I recommend replacing all lug screws to ensure they match in resistance. Mixing screws could lead to one having more resistance = more heat. Lug screws include integrated lock washer & washer.
M4 Fits all the smaller controllers including: ND72V35A, ND72V50A, ND72200 - ND72300
M6 Fits all of the medium controllers including: ND72360, ND72450, ND72530, ND72680, ND72890, and ND721000
