Andersen Ultimate Issues

That pinbbox is just freaky. That is likely the culprit for all the other issues you mentioned. The fact that it essentially self-destructed would have me extremely upset with the manufacturer. I know that it would appear that the 2 set screws hold all the weigh, but the lateral forces against the kingpin are pretty significant as well. There's a lot of people towing with the Andersen, yet this is the first reported issue along these lines I'm aware of. Not trying to be critical, just saying that the pinbox is obviously majorly deficient.

Though it doesn't matter to you any longer, you could use a crows foot adapter to tighten the bolt after setting the trailer on it ;-)