Just in case anyone would like to know, I think I figured it out.
I took the seat back off the other working headrest and looked at it. It appears that the motor just stops turning due to force. My advice to all is when adjusting the headrest, back it off from max up or down by a hair, this releases a great deal of tension on both the plastic gear mechanism and the cable that connects to the motor. Could save headaches down the road.