[JRTJH]

This is not a solution and also is not fingerpointing.....

Here is the situation as I believe it was reported.

1. A CURT receiver cracked at the edges (corners) of the receiver tube. This area is reinforced with a second layer of steel welded around the outer margins of the receiver tube.
2. A second CURT receiver, after one use, cracked in the same location at the corners of the receiver tube.

I'd be very suspicious of the "stinger" on the hitch that is being inserted into the receiver tube. It seems very suspicious to me that two receiver tubes cracked in the same location, one of them after one use.

Keep in mind that those CURT receiver tubes are used on thousands of hitches (many with different mounting brackets on multiple types of tow vehicles) without a failure being reported, and here's two in a row, one after a single use.

Something is "fishy" and I would look for a problem with the parts that "touch the receiver tube" to be sure they aren't causing the problem.