Most model airplanes have the motor in the front, which means that in a nose-dive crash (with the nose down) the motor may suffer. The most common damage is bending the motor shaft. A bent shaft means poor motor performance, high current consumption and will generate a high vibration level.
Now there is a replacement shaft for your brushless outrunner motor ROXXY 2830/ 12 and 2830/ 16 which can be changed easily and the motor will work like before the crash, no vibrations and no reduced performance.