Electric trailer brakes sticking

Is it also possible the brake pedal switch is not reliably disconnecting the circuit when the pedal is released? Can you see the reflection of your brake lights well enough in the front of your camper to see that they turn off as soon as you let go of the pedal every time?

While I agree with budwich's solution, mine is much simpler and will test your brakes under the same conditions that you described.

And as budwich said, don't toss your controller unless you have a technically verified reason to do so.

Actually, you don't have to do much IF you can duplicate your problem while standing still (ie. tap brake and it doesn't release... as "quoted").

go to your breakaway switch, pull the activator "finger"... do the brakes work? Good. Do they "stop working" once you put the activator back in? If not, you have a physical brake issue... cause there is no power going to them and the electrics won't hold if the power is gone (check by jacking one side of trailer to be able to spin wheel).

Once you have done the above to verify things in terms of wiring, then you can move on. Disconnect the trailer battery so that it CAN'T operate the brakes when the breakaway switch is pulled.
Now, connect the trailer to your truck. Activate the break away switch.... nothing should happen. IF the brakes operate, you have wiring issues.
Next, assuming that the brakes DID NOT operate with the breakaway switch, tap or manually activate your brakes at the truck until you are able to duplicate the "sticking". IF you get it to stick (again verify by spinning the "free hanging wheel"), then get a meter and touch the inside of the breakaway switch (where the finger goes in) to touch the contact (of course, the other meter lead is on ground). IF you see voltage there, then some point is providing voltage / power to your brakes... likely the controller. You can go from there.

My first guess is that you have a physical brake issue (seized, broken spring, etc)... but the test that I outlined will help determine if its electrical or mechanical.... without cutting or disturbing any wiring. Good hunting.

PS. people are going to tell you to just toss the controller and get a better / new one... problem solved ... maybe / likely.

One way would be to temporally spice a wire into your brake wire AFTER the plug connector. Run this long wire into your TV to the plus side of a voltmeter. Put the black wire of the voltmeter to any unpainted metal surface or use a jumper to connect to the outside of a 12V auxiliary plug. Drive around a while and see if the voltage follows your braking actions. If so, you have mechanical problems. If not, replace your controller.