If it's like mine there should be 2 wire nuts about 6 inches from the motor. Take those off and separate the wires. Hook your jumper cables directly to those wires and your trailer battery. Positive to one wire negative to the other. It will spark when hooking up. To go the other direction switch the positive and negative.
This will tell you if the motor is the problem. If it runs strong with the jumper cables the motor is fine and either lubrication or poor wiring is your issue.
Mine started blowing fuses when it ran slow. My guess is you don't have a fuse inline or it would be blowing. It sounds more like the motor is hitting it's heat maximum and shutting down. Definitely look up how to lube the landing gear and check the wiring connections.