Freerchobby motors suffer from this problem worse than other motors it seems like. The 63100 form factor just screams to exacerbate this design flaw. On other motors I have done this to fix the problem:
The first two ways tackle rotational slip only. (The axle still could slip out of the rotor) The third way, the dutch pin with the tapped axle, combats both rotational slippage and lateral shaft slippage like you show above with your new motors.