It could also be that the coupler latch is not tight enough. You can adjust how tight the coupler jaw engages against the ball. There is a nut that tightens against a spring which pushes the jaw against the ball. If not tight enough when hitting a bump or pot hole, with enough upward force the coupler can be snatched right off the ball even with the coupler pin in place. It might not have been set tight enough at the factory. The dealer should have checked it when setting up the WDH when you bought it. Then you should have checked it before driving off the lot. If you installed it, you should have checked it.
This happened to a friend of mine. He borrowed my utility trailer to take his Harley to Florida when he took his wife to visit her mother and stepfather. He wanted to ride his Harley on the beach down there. He came over a hill in NC with no warning that there was a construction site starting. He hit a big bump and the rear of the trailer went about 30 degrees into the air. When it bounced on the tires it came off the ball. The tongue went under the back of the TV and rested on the safety chains and wiring harness while dragging on the pavement. He ground through the wires and almost through the chains before he finally got it stopped on the shoulder. No damage to the TV or Harley. After he got it rehitched he took it slow and easy to the nearest Walmart for a new chain and some butt connectors for the wiring. The coupler was tight enough for normal towing, but not for 1500 lbs of trailer and Harley going airborne.
When I bought my 28 ft TT new, it was the first time I ever used a WDH, since it was the largest trailer I ever owned.
I got it home and unhitched in the street so I could turn around and use the front hitch to push it in the yard, I found out the guy that set up the WDH forgot to tighten the nut on the ball for the hitch head. The only reason I made it home after 8 miles on the interstate and 4 miles on city streets was that the WDH spring bars kept enough downward force that the ball stayed in place. The nut must have been finger tight when I left the dealer. It was almost to the end of the threaded shank when I uncoupled at home
It was the guys fault for not tightening and torquing the nut, but I'm partly to blame. I should have checked the ball and everything else as he showed me how to hook everything up instead of just watching. I would have found the loose nut.
