Hi Alex, can you please post the new .dxf file you generated from moI with the FlipNegativeZAxisCirclesAndArcs=y set so I can double check it?

> just made me wonder if tangency did have a finite point in the transition from arc to arc.

It doesn't seem like that's the problem, the arcs seem to be tangent to a very tight tolerance. It's more likely to be some difference in ordering or directions.

- Michael