mask on ark problem

[forrey45]

Using the mask on ark to pick hole positions, view in isometric with a new drill it will only pick six of the twenty four arks not even the one that is used to set the diameter but if I change to top view it will work OK and pick all the arks and yet on a different job it would not work even with a top view. If I use a different computer no problem this would suggest a setting out of whack but what it is I have not been able to work out. One of the jobs was a solid and the other just a 2D. I am stumped, any ideas any one!!.
I had three jobs come back off the floor to-day missing one hole in each (thank goodness for good set up guys).
X5 MU1
Thanks. Forrey.

[txcncman]

First, it is arc, not ark. Second, you really should post the actual part file you are working on to get a reasonable answer. Are you working with a solid? Are all of the arcs on the same plane? Are all of the arcs on the same face? Just because you can see them in Wireframe does not mean MasterCAM can "see" them if it is a solid. A work around is to create curve on one edge on a new layer, then turn all other layers off before selecting.