Trailer problem

For some reason I can’t figure out when backing up my boat trailer the breaks lock up.
They are surge breaks and the only way I can get them to work is to jerk forward and slow down slowly before attempting to back up. Rig is three years old and no problems till this. Do I just need to spray lube or is there some other fix required? In order to back into garage I had to tape up the small key to prevent the slide mechanics from engaging the breaks.

Are your brakes suppose to shut off when the backup lights come on? Might want to check the fuses in your vehicle. I carry a C clamp instead of the key. Much easier to use.

The blue wire on the plug if you have it is to disengage the brakes when backing up, it works off the reverse light. If you have the 5 pin connector put a DVM on it and have someone put the truck in reverse and see if you have power, should be a easy fix

I had the Same problem with my old trailer on my bass boat and it was just where it moves/slides it was rusted pretty bad. A little pb blaster and all was good.
Than I sold the boat a year later