Big problem-- people using the APC props incorrectly.
These props can be bent hard without showing physical signs of stress -
Stressed plastics are invitations to failure .
I have never had a seconds problem with the APC props -up to inc 20"dia.
But some guys can screw up a wet dream--
I gave some small electric props to a guy for his tiny 370 Eflight motor .
he called me to tell me the last of the props had broken on "hard landing" but that super glue I gave him also worked to glue the hub and blades back together and it worked !
True story --
in late 1980s the slick new prop was a light green plastic prop -for pattern flying -- I loaned one of my friends, a plane to practice for the TOC and he came back to the house with the plane in one hand and the motor and nose section in the other -
the prop had simply exploded in the air and he landed it sans entire nose section (tricky).

How plastic props are formulated and cast means a lot - these particular ones showed stress lines fairly easily but the hub section was hidden by the spinner ---