I don't know how the CRT is built but it could be something to do with the chassis and the way the center diff is mounted causing flex as well. Shocking to me to see a 5mm shaft break so quickly.
I always suport the RR of the motor with a block of plastic between the motor & chassis . This way the weight of the motor wont cause the mount to flex under a hard landing . I do this in all my cars that have a big neu motor . Look at the six picture to see what im talking about .