Help us by letting us know which RV you have. Also which TV and brake controller you have.
Having said that, if you haven't pulled the hubs and inspected the brakes to see if they have grease on them, I suggest you do so.
If they don't have any grease on them go through all the connections between the truck and brake magnets and check them. I'd just remake them even if they looked good. Don't forget the ones in the junction box. Then check and clean the 7-way connector on the truck and RV.
Salem 29RKSS Pushing a GMC Sierra 2500HD!
Gotta go campin!