I see two issues where there should be none: The sway bar bracket cracking, and the area around where the sway bay attaches to the floor cracking and detaching it self from the floor. The steel (bracket material) is weak and cracks. The steel (floor material) is weak and cracks from stress applied by well attached brackets. It would say there is an issue with the material (steel) used to make the brackets and or floor sheet metal. The force (at the rubber bushing) on the sway bar should be simply rotational on an axis across the car. The OE sway bar has 2 pivot axes built into it to alleviate any other force, the pivot axis of the link at the control arm is lengthwise on the car and the pivot axis on the sway bar end of the link matches the sway bar bushing, across the car. Sway bar links that are shot to hell (severe binding) could change this equation somewhat. It would be interesting to see if the VINs of the cars affected are clumped together or not. If they were that would also point to a materials issue.