The GM R4 compressor is built with a center aluminum casting then a steel tube slides over the OD , a o ring trapped between the body and tube on each side is used for sealing. Improper mounting leads to the tube sliding off the body, apparently only on MB cars as I've never seen this on a GM car

Overpressure and missing hardware is hardly the compressors fault, it's like overloading a car with weight, having a tire blow out then blaming the tire.