Denford Software & Machines

I am trying to cut out cars for F-1 schools. The VR Milling 2D/3D simulation shows the car being cut out perfectly. There is also plenty of buffer room between the cut path and the metal fork/metal claw in the 2600 Router. However when I go to actually cut out the car with the 2600 Router. The tool randomly deviates from the simulated cut path and cuts into the front metal claw of the machine. Any suggestions on how to fix this problem?

It sounds like the machine is stalling (the stepper motors think they have stepped around but something prevents them from doing so..either a tight slideway, screw or the material is too hard, tool blunt, travel too fast...)
Can you post a photo of what's happening ?
Have you lubricated the slideways and screw recently? Also be aware that dust build up can stop the axes moving freely.