As JohnKSa indicated, the physical evidence described by the OP strongly tilts the scales toward an overpressure round.
And, though the OP says he doesn't reload or mix ammo, he has extractor marks on at least one of his rounds in the photo he provided. So perhaps the OP is in the habit of frequently rechambering his factory rounds, which can lead to setback and overpressure.
And, as Tamara noted, depending on the age of his ammo, he may have some from a timeframe when FC .40 was known to kaboom from inadequate case thickness.
NONE of the evidence provided or described by the OP indicates a failure of the weapon itself. If anything, it sounds like the weapon did its job - the OP did not describe loss of fingers, or suffering of shrapnel related injuries.