My engineering colleagues have explained that this type of gear wheel is made of a steel that has rather a severe crack propagation characteristic and as such the failure mode is severe and is exacerbated by the lack of debris created during the failure process. This lack of debris leaves the airworthiness of the component design open to question as there is no effective way of preventing ultimate failure once cracks have appeared.
You may well ask how we progress from here. It rather looks as if the edge of the carpet has been raised and the offending question swept under it. A large notice stating DO NOT GO HERE has been stuck in the ground by the EASA lawyers who appear to have wagged at large and menacing finger at the brave chaps and chapesses in the UK and Norwegian CAA.
G