I suspect that SEE with really low charges is a similar phenomenon. The bullet begins to accelerate but pressure drops rapidly and the bullet's acceleration (not necessarily speed) drops off. The shockwave catches up and a localized ultra-high pressure event is triggered, which propagates through the remaining powder and "BOOM!" It just happens very close to the chamber instead of at the far end of the barrel.
As I pointed out earlier...If this is real, then you'd think this amazing equipment and software would be seeing anomalous/extreme events at the chamber, even if they do not end in catastrophic failure...