If only one hub gets hot, the first thing is check the adjustment of the brake pads. Second is to check the ground wires. I just fixed a weak ground on my trailer which is a very common problem as the ground connections corrode, just like on the top of a battery. Third, fix the wire in the picture. That will eliminate any concerns. I always solder trailer wire connections. If it still pulsates, pull the hubs. There might be a mechanical problem. If that's easy for you to do, I'd do it first.
Me, Julie, Lil' Barry, Faith, and OSDs, Fang and Treaty
2003 Hyundai Starex (H1), 2012 Coachmen Clipper 126
I don't know when we'll be able to go camping again...