Help diagnosing HappiJac issues camper jacks and remote

I think it is indeed highly likely that the problem will be in the connection plug. I would get some electrical spray and spray the connections, working them in and out and spray again. The proper spray dries fast and cleans too.

You should also check the main feed wires. They are heavily loaded wires when the motor is lifting, and a loose connection in the main feed could easily cause your problems too.