Here are some more tips, additionally to our Online-Help and manual:
B. Concerning contour correction
If a contour has a slit, the mill must not be broader than the slit, more exactly: the diameter of the mill must be at least 0.2mm smaller than the width of the slit; otherwise, the corrected contour will not be generated.Normally the contour is done very well, if the contour consists of a series of lines resp. of a polygon. There can be combinations of arcs where no clear mathematical solution is possible, the error message will appear "contour correction not possible".With succeeding arcs it may be helpful to generate succeeding lines (instead of arcs) by "thin out contour" and to apply contour correction then.