Has anyone mentioned...
Whenever I hitch up a ball hitch, I'll connect everything like I expect and then I'll crank up the camper using the tongue jack to put force between the ball and coupler to see if they pop apart.
I had a golf cart trailer (rental cart + their trailer) come off of my truck when I went to ride the 6-person cart up the ramp. Scared the hell out of me. Fortunately 3-4 big college guys came out and helped me lift it back onto the ball and someone familiar with ball trailers helped me get it hitched properly. From there forward, I always raise the trailer to try and force it to disconnect.. kind of like a fifth wheel pull-test.