Been there done that when bringing home a brand new trailer @ 65 MPH in the left lane on the interstate. The pigtail was a frayed ball of wire and all 4 trailer tires locked up. I managed to drag it to the emergency lane and sort through the wire mess and get the brakes released and everything working again.
I drove to the next exit, turned around and took it back to the dealer for a new pigtail and 4 new tires since mine all had serious flat spots.
I walked into the dealership service dept red faced and explained what had happened. They changed the pigtail for free and gave me a seriously good price on the tires. I felt they went above and beyond since I was the dummy that hooked it up.