Been there, done that. While hitching up the fiver, the pin dropped in the open jaws of the hitch, & no matter what I did the jaws would not close. This is where I got brain freeze that I can't explain. The landing gear was up, & I decided that if I backed up a little it would send the pin home, & the jaws would close. I removed the chocks from the trailer wheels, & closed the tail gate, got in the truck, with my brain still frozen, & backed up. Well we all know that the jaws didn't close, & when I stepped on the brake the trailer continued to roll, off the hitch plate, & onto the bed of the truck. When that happened we had been towing the fiver for 7 years. That one cost Allstate over 5K.
John