Brushless motor suicide!?

[jimmy]

I did a couple of laps of practice on sunday with the 4WD and LRP sphere (non comp) with a 3* motor. and the pinion was a bad fit for some reason, it would barely reach the spur but I thought nothing of it and got a fairly decent mesh anyway.

I set off for my practice anyway and only did a couple of laps before the car just stopped.. The pinion had come completely away from the spur (and chewed it up), the entire motor shaft had loosened from the magnet and punched out of the back of the motor!

I looked at a 4* that someone donated and it had a larger diameter shaft (inside the can) even though it's a similar looking motor - not the newest X11 style.
Is this a common problem, and is there anything I can do? Do LRP/Helger fix this problem or am I just out a motor?
It's nothing I've done, I don't drive fast enough to hurt motors.