You are referring to the pawl. The pawl has thread on one side only - not both. I think you are tightening the hex screw into the side of the pawl with the thread. Turn the pawl over, and refit.

A simple test is to remove the pawl and insert the hex head to determine which side has the thread. The side with the thread must face AWAY from the hex head - so you are clamping the flipper shaft.