I have the blad runner kit but am still building... but CNC and machine building are not new to me.. I think I may have seen your post on yahoo groups site.. anyway. Couple things I would look at trying to diagnois.. the 2 motors in question that are loosing step. swap them( meaning the cables first) Then the physical motors... and see if you loose the step to the opposite side. if so I would then look at that indavidual motor or signal. Also look for any drag on your table a stepper motor can loose it self if you have some binding going on... just some thought.