Looks like someone welded something in the torque tube hole. Probably to prevent it from punching a hole in the casting penetrating into the differential cavity.
Gave a visual check of both sides of the trailer at every stop, on the way up and on the way back. No signs of a leaning wheel or loose lug bolts at least visual to the eye.
Does anyone have experience in determining the cause of such a thing on a single axle trailer, not overloaded?
No perceptable warning given, just boom and tire, rim, and lug bolts and nuts gone.
Whew