Hi Rudy, this usually means that either the curve is not planar (not the problem in this case though), or is not closed (this is the case here), or has a self-intersection in it, like a little curly-cue (this is also a problem here).

Here is the problem area:





(I moved the points slightly to the left and right above so you could see more of the shape)

That area of the offset did not go well, the ends sort of overlapped over top of each other instead of getting cleanly trimmed to meet up nicely.

This area will need to be cleaned up by something like trimming out that spot and drawing in a new piece to close it up.

It would be nice if offset did not produce this, but it is very difficult calculation for offset to get a good intersection between 2 pieces that intersect at a very shallow angle. Your original curve is not quite tangent in spot, it is about 1 degree off. This makes a little gap in the offset that needs to be filled in, and that is the part that is having problems in this case.

If you can make your original curve be more precisely tangent, it will help to make a cleaner offset. To do this, the first inside points for each segment should be lined up right on a straight line with each other.

I'm thinking of tuning up Join for V2 so that it will automatically "true up" tangents of adjacent segments that are within a small angle of each other to avoid this kind of problem.

- Michael