BIL with Superglide drops his trailer

During the summer, I hooked with my Superglide, did a test pull, then pulled out of the park. I had to stop and start at the gate then at a red light. Drove 2 miles stopped and started again, then drove 43 miles to the exit I was taking when my fiver came loose landing in the bed of the truck.

I have not figured out what went wrong but I now have an Andersen