Hi David, also there is one other problem in your original curve - there is a small region of the curve that has a tiny "curly-cue" self-intersection spot in it:





So notice there after zooming in that there is a little odd piece that sticks out extra? That's not good.

Basically any messy areas in your original curve like this will then become messy areas in the solids which will then be difficult for the intersection algorithms to resolve.

- Michael