> Is that then just a connection problem on the offset curve (just interested)?

Yup, basically each segment is offset - if the segments were exactly tangent with each other, then the offset segments will touch each other exactly and can just be easily joined.

But if the tangents are different between the 2 segments, then the offsets will have either a gap between them, or cross each other.

Gaps are filled in by putting in a kind of extension piece - this is what is controlled by the "Corners" option.

The part that tends to be more difficult is when the pieces cross - then they have to be intersected and the excess part trimmed away. Intersections of things that are small and/or nearly colinear tend to be difficult to calculate.

- Michael