When trimming down I sometime hear a popping/grinding sound like the trim is in a bind. This does not happen every time and when it does occur it does not matter whether I turn the motor either way - I checked the motor and it seems the motor is scraping the left side of the trim housing more than on the right. It does not appear to be severe - just noticeably more wear. Does anybody have any thoughts as to why I would be experience this issue.