The shaft that connects the motor to the x axis pulley is the one which has managed to move through the bearings so that the coupling was rubbing against the motor mount.
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A picture of the complete motor mount. I didnt think that the shaft would travel through the bearings so I didnt fit any locking collars. I will make them and fit them on the motor side of the last BK mount before the pulley. This will stop any further movement.
I suspect this has been caused by the pull on the shaft from the tension on the pulley belt but this is a guess. Seeing as I had to hammer the shaft through the bearings I really didnt think it would move.

Ian