Are you using the Vector Validator option to locate the problem areas?If they won't join its probably an indication that the entities are located in such a way that you are asking them to do the impossible.I can't remember if there is a tangent snap option in Vcarve.If not you may need to draw the straight lines in their desired location and then use the fillet option to create the radii as this ensures the entities are in contact and I believe it also joins all three entities (the two lines and the radius).If you try to cut an outline that isn't joined,the machine is likely to behave in the manner you describe as it may default to left or right of the vector and will define that side from the order of creating the endpoints.