I just purchased an AR with a Daniels Defense Upper and it has an American Tactical GB1-A522 adjustable gas block. I took the rifle out to fire and it only fired single shot. I tried to turn the knurled knob on the GB1 and it wouldn't move in any direction. The spring loaded detent depresses fine. I loosened the mounting screws and removed the rod and the knob still doesn't move even after applying some penetrating fluid. Can anyone give me a heads up what I may be doing wrong or what I may need to do? I don't want to force it and damage it. Semper Fi