1 cube N42 neo magnet to suit X.03 & X.04 motors. N42 has a greater magnetic force than N35.  These do not suit the bogie motor with the twin worms.  

 Replace your original magnet with this to help revitalise your motor.  Test the motor with your original magnet to see which way it rotates.  Install this and check again.  If the motor rotates in the reverse direction to previous, just take this one out and put in again facing the opposite direction.