It's pretty easy to adjust a hitch to fit the ball, but it'll still move around a bit. In fact, I've never purchased a trailer that was adjusted properly. There's always some slop, if only for rotational movement on all three axis. I've had the same thing happen, though didn't lose the hitch, but did feel it yanking at the ball, so I stopped and it was nearly lose enough to have popped off. Yep, a good solid downward force on the ball solves this and she'll trailer better. Light boats don't put a lot of torque on the ball/hitch, so you can get lots of wear out of it, but heavy rigs quickly show where you need to address stuff.