I am trying to install a new power mast on my motor. I was able to remove the old mast and broken nylon cord from the motor. When I install a new mast I turn on the radio to run the motor up until it stops. Then I start the cord in the teeth and turn the radio off. The antenna will go down all the way but an inch. There is no cord previously in the motor. If I try to help the mast down in any way while it is retracting it breaks the new cord. I have went through 2 masts now. These are Ebay masts but I did not think they were the issue. The motor has a lot of torque and does not seem to slip. Have you heard of this and what do you suggest? I would like to keep the factory motor.