Are the brakes not working at all, or just not as good as should be when connected to your truck?

Maybe your truck wiring is suppling the backup solenoid with 12V in error?

Back up solenoids are a Pain. If the trailer moves just a little once the truck is stopped, (before you put it in reverse) the brakes apply. My solution is a C clamp put on the surge brake housing to stop the hitch side of the assembly from compressing when I back up. I do this at the ramp when I am loading and removing the straps.

That's a good idea.

Then you are unfamiliar of the pressure relieving models. They are only $10 or so more. plus you don't have to jump out in traffic to put a clamp on your coupler in those occasions that happen at the worst time. :) been there done that. But you are correct on the plain version can be a pain. You should look into the deluxe model well worth the time to nstall