broken Rotor CC Neu 2200kv

this weekend i was racing.
environment temperatur was 18°C and my motor was never higher than 50°C (dx3s shows me)

on a long straight the car do a full braking and i cant go on.

a check shows that the motor is blocked.

i pulled down the front motor cover and try to get the rotor out.
this was very hard (not because the magnet)

and i saw the rotor was broken, here is a pic:



what could be the cause for this?
is this a case for warrantee?
i hope so.

x2 crt, 6s lipo, castle combo 2200kv, geared to 62km/h, 11t pinion.