Hi Mike, so like Burr mentioned that may mean that the first time you did it you used a curve made up of several segment pieces as part of the construction. Curves made up of several sub segments will generally transmit those segments to things constructed or cut from them.

When you use the Join command, it's really sort of like a kind of grouping where you can still revert to the previous segments by using Separate. The rebuild command can help to merge 2 smooth segments together into a single larger segment if that's what you need.

- Michael