If that exact cause is not genuinely identified....
The cause is that the orbital gear cannot contain a disassembling planetary gear. Containment is not new; I've flown helicopters with a containment ring around the turbines to stop them destroying the other engine and hydraulics.
The problem with the existing gearbox is that there is only one failure path; that goes and you are dead. It is IMHO impossible to guarantee that any gear assembly will last it's planned overhaul life however long you test it.
The 330 and 332 got away with it because the design of the gearbox had sufficient reserves. You pile in more torque and strain on affectively the same bottle then something has to go. I cannot see any other way than a complete redesign with multiple failure paths within the gearbox.
History may prove that this way will be the standard in the future.