According to our resident FCA tech, the defective lifters have soft (improperly hardened) pins or wheels that develop grooves in them that ultimately cause the needles to pile-up and stop rolling, and, as soon as that happens, the 'ol SADI camshaft says goodbye to its surface-hardened lobe. This is supported by the evidence I've seen where some of the lifters that have failed aren't the MDS ones, rather, they are the normal lifters.Probably talking about the poor engineering choice of using a SADI core with a roller lifter that has a practically designed-in tendency to bounce on the lobe, causing damage to the roller, spalling of the lobe, and/or general failure after ingesting enough of its own parts
IMO essentially every "green" technology they've introduced to save fuel (DoD, MDS, VVT, AFM, kitchen sink, etc) have so negatively affected the reliability of previously solid engine designs that it's an absolute guarantee the owner has wasted more energy fixing their vehicle than the green technology would ever have saved! We have failed cams. Failed lifters. Failed phasers. No way were these technologies a net win for the consumer!
GM appears to suffer from the same issue, despite using billet cores, and if anything, the issue is even more prevalent.