Either a 600 or 900 model. Your problem could very well be your contactor (solenoid) or the motor/driveshaft assembly could be getting tired. The mtr/drvshft assembly is the little gear that engages the motor. if it gets stretched out, (very hard to detect) or locks up, ( the litlle gear should rotate no more than 1/4 turn) it will lock up the windlass. unfortunately this little bugger costs $132.10. it is the most common problem with the Horizons.
this gear runs in a cutch bearing that lives in the motor endcap. this too can lock you up if it fails. If you need repair send it to me at Florida Rigging & Hydraulics. (blatent commercial post lol)

fair winds,
Buk