From the accident report REDL. My take away is the reticence to use the aircraft may very well be the inability to show what was the initiator of the failure.
An extensive and complex investigation revealed that the failure of the MGB initiated in one of the eight second stage planet gears in the epicyclic module. The planet gear had fractured as a result of a fatigue crack, the precise origin of which could not be determined. However, analysis indicated that this is likely to have occurred in the loaded area of the planet gear bearing outer race.
A metallic particle had been discovered on the epicyclic chip detector during maintenance on 25 March 2009, some 36 flying hours prior to the accident. This was the only indication of the impending failure of the second stage planet gear. The lack of damage on the recovered areas of the bearing outer race indicated that the initiation was not entirely consistent with the understood characteristics of spalling. The possibility of a material defect in the planet gear or damage due to the presence of foreign object debris could not be discounted.
Because the root cause of this accident has not yet been identified, it has not been possible to identify a terminating airworthiness action with respect of the failure mode experienced by G-REDL.
The use of "could not be determined", "likely", "possibility" do not engender confidence.