I don't like ball couplers for that reason. I think there's a inherent design problem with the pressed steel couplers that the manufacturers probably buy because they're cheap. I can't count the times, the coupler hasn't seated because the keeper, or whatever they call it, is too far forward and lodges on the top side of the ball.
For someone who doesn't know, the coupler may look like it's seated on the ball but it isn't. There's one trailer on the place that still has a ball coupler. I went to the trouble of replacing it and found the problem still existed. They need to come up with a design that has a more positive working latch. If the latch isn't locked, the keeper isn't in a position to ride up on the ball. It should be totally clear of the ball until the latch is activated. That trailer doesn't go off the place.
Because of the ball coupler problem, all of the other trailers have lunettes. There's no mistaking when a lunette is properly attached to the pintle. FWIW, Northern Power started carrying the multi-postion channel with attachments, so a trailer with a regular coupler could be setup with the choice of a lunette or if you just had to have it, a ball coupler. It's on page 284 of the latest catalog. That's the setup I speced on my dump trailer. On the road, I use the lunette. On the farm, I can convert to the clevis.
To convert you'd have to do some welding, but you'd never lose a trailer again. When you factor in the potential damages from a runaway trailer, the cost of conversion is cheap. The other thing I do because I don't trust safety chains, I see too many of them dragging on the ground, is to use cable ties betwen the links to make sure the hook can't shake loose.
