In the case of G-REDL the failed gear was propelled like a knife through the casing. That hasn't happened here it seems (the AIB had the epicylic casing in the shed in Bergen).
If the MGB seized totally either the shaft would surely fail in torsion or the splines would be torn off. There is no sign of that or of the tail drive shaft flailing after a sudden stoppage. If there damage like that it is difficult to imagine the AIB would not have said.
Does that mean we can conclude what happened?
No.
Only a fool would try to draw conclusions publicaly on cause second hand.
However I can see how a possible suspension bar attachment failure is worth an AD especially as one servo (the front one) separated and most of the front suspension bar is missing.
Does anyone know if any problems have been found in the rest of the fleet following the AD?
And what news of Shell Norway's action against CHC?