LSMAN

I have an Airstream as well. (On my 4th one). When I purchased my truck remotely in march 2020 and the dealer delivered it (2020 RST) , There was no brake controller for towing. I made it very clear that I have an airstream and the sales guy apologized for mistake. His boss allowed him to purchase an aftermarket controller for me. it was ordered and sent to me- I installed it. Looks factory. (I installed something similar an aftermarket controller in my 06 Silverado for my 1966 Airstream) Sorry if I missed the obvious here but does your truck have a factory brake controller? If not you need one. If it does have a controller her is what I would do: Check the grounds on both the trailer and the truck. Bad Grounds cause most problems. With trailer unhooked from truck use a 12 volt battery and power up the trailer lights individually: running lights, brake lights electric brakes. Verify that the problem is not on the trailer side first. make sure that you do not power up the emergency brake pull. If engage for long period powering this will burn up that (plunger switch with cable.) LED lights will not cause the above problem.

On my 2020 RST The radio is also staying on after truck is turned off and drivers door open. The door opening use to trigger all systems to shut down. Earlier this week one morning the remote start feature would not work on key fab. Probably due to the truck is still powered up in someway? I Wonder what else is still staying powered on? This can not be good for the battery. I went in and scrolled for a way to click on an "update software" but that option was greyed out and not possible so I guess they have to send one first? Don't the GM engineers and marketing folks at GM read through these forums? Please send a software update for this problem!!