It's rare for sure but can happen.
I don't disagree, as anything built by man will inevitably fail, but you seem to be experiencing more than your share of failures?
And I'm not there, but if I might envision: perhaps your car wheel stands, violently dropping the front suspension and coupled with longer than standard O.E.M. as engineered travel capability, coupled with the more rigid polyurethane bushings this may lead to a resultant bending motion of the drag-link bar?
It's definitely a less than ideal suspension engineering execution, and a bar with a hinge might solve one problem; but I'm just saying be prepared for new problems when one component is changed to something different than that as originally intended and the resultant effects to the surrounding is not considered, including when the vehicle is utilized in a fashion other than as originally intended also.
Scott.