You may have worn down the locking compound on the set screw. This usually happens if the adapter was tightened using an Allen key via the set screw. The set screw is not for tightening the adapter down - it's only for logo adjustment. The correct way to tighten the adapter is by using a 16mm wrench. If you have worn down the set screw locking compound, you can use some plumbers tape or Loctite. Alternatively, you can order some replacement set screws from us directly. Please visit our help section to view all of our adapter installation guides.