First, let me ask if I have the most recent version of 10 - mine is 10.0.1006. My problem is that when I do a sequence of 4 Drill&Tap grid operations, CAM becomes confused and holes end up in the wrong locations and sometimes the wrong size. This is not a post problem - the error is there when CAM simulates the run. With the Mach3 post, it generates code that is consistent with the incorrect CAM simulation. I have a file that demonstrates this problem, but I am not sure how to share it on this forum.