My two cents worth:

Both blade failures appear to be fatigue related, not overload per se. The breaks are clean, and there is evidence of crack propogation. High RPM caused final failure as the cracks spread. Fatigue is related to operating RPM - especially dangerous if you transition slowly through critical flex frequency of the blades, ESPECIALLY bad if critical frequency is at or near full operational speed. Relatively small root section vs. heavy blade (as in the case of both of these MA props) lowers critical frequency, putting more fatigue stress flex cycles on the blades as prop goes from idle to full load.

The section area at the breaks is relatively small when compared to other well designed glass reinforced props such as APC.

MA props are not very efficient aerodynamically. Propeller efficiency of any APC prop compared to "equivalent" MA is noticeably higher. I have compared them in the air, and the aircraft performance is noticeably better with the APC. This, along with the apparent danger associated with MA props should convince anyone to use APC, not MA.

MA props do have their place. I use mine for stirring paint and large batches of epoxy. Literally. I would not mount one on the crakshaft of a model engine any longer.