Poorboy, you nailed it, too much penetration and you have a very nice warped housing, too little ,and you get to post on Moparts.
Its also the perfect storm for warpage, all the welding on one side only of a tube , and with a thicker piece of steel that needs more heat then base metal for welding
The weld IMO should have been wrapped around the perch ends, and I suspect this weld failure was visible upon close inspection over time, there was a warning/
the main lesson here, check all welds, regularly, if the are important..
Nobody is perfect.