Now that the focus is squarely on the planet gears, investigators will doubtless be looking into all aspects of their design, manufacture, assembly and operation.
I am just going to throw this speculative idea up in the air for consideration.
Is it possible there may have been hydrogen embrittlement of the gear material? I noted from AAIB report 2-2011 that the carburised gear raceway is chemically etched before final polishing.
I am not a materials specialist but I wonder if a combination of materials susceptibility, environment and stress have combined with the presence of diffused hydrogen trapped underneath the carburised layer to initiate a defect and cyclic stress has done the rest? Spalling might or might not occur.