I had an experience with my Lewmar windlass.
The first dey on a ten day cruise was a long one and we planned to anchor for the night. Found a spot, intied the line that secures the anchor while underway and hit the "down" switch. Nothing but a soft clicking sound from the windlass. Tried a few time, tried the other direction, nothing but a click.
Faced with the choice of manually dropping the anchor and manually retrieving it in the morning or continuing on to a marina, we chose the latter.
At the marina, I took the side cover off, removed one of the gears and determined thaat the motor was getting power (the click) but was not turning. In fact, it couldn't turn, it was rusted in place.
I put a trusty pair of locking pliers on it and wiggled it back and forth until I broke it free. I tried the switch and it ran both directions.
I cleaned up the inside of the gearbox as best I could, put grease and oil where I could, put the gear back on and closed the case.
I tested it and it worked in both directions and it worked for the rest of the trip. Later, at home, I took it apart again and did a more thorough job of cleaning and lubricating.
Apparently, the case is not watertight and you're supposed to take it apart and clean and lubricate it from time to time. I'm thinking it would be worth it to take it to a pro for this as long as it's installed with this in mind i.e. posts and terminals for electrical connections.