Sounds as if the threads closest to the edge of the case are buggered up. Try two nuts tightened against each other and back the stud out. Then clean the hole threads with Naptha using a q-tip and clean the stud. Apply some lock-tight (red kind) and tread it in and let it set over night. had to do that with the stud I was missing.
Allen Caron
VW based 53MGTD - "MoneyPenny"
"If one thing matters, everything matters" - from the book The Shack