Hi Lemo, the biggest problem is when you have an overlap that is not totally precise.

Like for example when you do a sweep, the geometry is the result of a fitting process. When you have a shape like that hugging along something another shape that is just very slightly different, it causes the pieces to kind of dip in and out from each other. It makes it hard for the boolean code to determine a clean intersection.

If you run into these, please send them to me, it is hard for me to make improvements without having examples to work with.

- Michael