Originally Posted by
ihavenofish
that clamp is definitely suspect. not enough support for such a big piece of wood id imagine. could explain why a heavy cut will move.
i think you have to go about this methodically, change one thing at a time. lock down the wood so it definitely cant move, then run again. if its still bad, then check if the motors are actually loosing position. marke 0/0 on the table with tape and a marker, and see if after the program is done it goes back to 0.
if no, then its going to be something wrong with the servo setup. it is either losing its place, or dropping steps from mach3.