Your boat is really keeping you busy, not?
For your problem I think you have two possibilities. A relative good one and a bad one.
The good one is that the relay is not working for whatever reason. I’m guessing the relays are near to the circuit breakers in the guest cabin (see attached circuit diagram).
The second possibility is that there is so much play on the gears inside the gearbox of the furling motor that they lock-up causing the motor to stall.
My first guess would be it is the first problem, maybe caused by a broken wire or contact corrosion.