First of all sorry for responding so lately to this topic, but I did learn some information about this incident recently. Apparently the propeller of one of the pods struck bottom or a submerged object. The QM2's propellers are stainless steel instead of bronze and don't flex very much on impact, thus causing the whole propeller shaft with rotor and bearings to be pushed up at least a few centimeters. This caused massive damage to both bearings and of course to the propulsion motor itself, which is according to my sources "melted"... I have no further information, but I would imagine that the propeller shaft seals have been misaligned leading to ingress of water into the pod.
BRGDS / foggy