We've had this trouble for quite a while when machining a pocket that has one of it's edges colinear with the edge of the part that we have to draw another line that is offset from the part edge. The problem with this is that it leaves the radii in the corners where we don't want them. Not sure if I explained that well enough...see the picture for an illustration.
We've never been able to do anything in sheetcam where we have overlapping lines. We cannot select different line segments, only an entire perimeter. In more complicated parts we have to suppress features in our models and import many .dxf files. This can be a pain, especially if we make any changes. Is there another way to machine these types of parts without redrawing the part every time we have overlapping lines?