i've not seen a fix for this....
the long bolts that screw in from the pinion end dont have much material to screw into inside the motor can and overtightening those bolts will strip the threads inside the motor...
IMHO its a design flaw in the x11 motors.
i've tried glueing the bolts and even glueing the entire front plate to the motor can but at best it lasted only a few minutes, but not a full race
maybe someone else has been more successful in a repair?
-Mark