Alpine 5th wheel: one brake locked up

[Thunk]

I've done some searching but haven't found a match for my symptoms yet:


2019 Keystone Alpine 5th wheel with about 6k miles on it. Was moving sites today and (luckily) just as we approached our exit the truck (Dodge Ram Cummins) threw an error to check the trailer brake wiring, followed by a warning that the trailer brakes were not operating. I had not touched the brake pedal for quite some time, and was not touching it when the error occurred. I squeezed the lever on the controller and felt the trailer tug me, so I knew at least some of the brakes were still working.


We exited and pulled into the campground, which was fortunately right off the interstate. When I walked around the trailer I found that the rear, passenger side brake on the 5th wheel was hot and smoking. The other three wheels appeared cool and normal. (I also confirmed that the emergency brake line hadn't been pulled. Although, I would have expected all wheels to have been dragging if it had).



I unplugged the brake line from the truck and re-plugged it. We checked in and moved to our space. That move was relatively short, but the wheel didn't seem to be dragging or heating back up. It's unclear to me if the brake has reset yet or not. I have not had a chance to pull the wheel yet (maybe tomorrow).



My questions is:


The Ram detected an error, but I'm not really sure how. I figure there's either a wiring problem that triggered the one brake or a mechanical issue that caused the brake to seize. The fact that the truck detected the condition seems like a clue as to what went wrong, but since I don't understand how the truck detected the error, I'm not sure what the clue is telling me.


As I understand it, on a 7-pin connector, 1 wire feeds all four brakes. So what is the the controller on the truck monitoring? Does anyone know, How did it detect that one wheel was (spontaneously) braking?


Thanks,


Thunk