As my job is running my x and y axis are slowly creeping towards negative values. For example: If I run a job for about 1/2 hour and then stop it and tell my machine to return to zero, it will return about 1/8" left and below its original zero point. This shows up if I am cutting a gear and the cutter is making multiple cuts around to get to finished depth. After a few passes, the cutter no longer passes through the same position as the previous pass. I am running 3-Axis NEMA23 CNC Kit (36V/9.7A/425oz-in/KL-4030) purchased from Automation Technology and running on Mach3. I am using cambam for g-code. Any suggestions?