When selecting the guide curve for a multi-axis curve toolpath on some of our parts, the following message occurs: "Propagation domain is empty". This prevents us from auto-chaining the guide curve, and forces us to manually select it. This is problematic for us as many of our parts have extreme curvatures and fragmented lines that are broken up, making the selection process prone to error. What is the meaning of this message and how do we correct it?