The set screw on the pinion gear has routed out a groove on the motor shaft and has made multiple indentions on the shaft, also. I think I may have over tightened the screw. Is there any way to fix this like replacing the shaft? I think it will continue to route out a groove until it is all of the way around. I am not going to tighten the screw as much, and hope for the best until I get it figures out. Thanks in advance.