Hi Andy, so I did a closer examination of these 2 curves here:



When building sweeps for them:



If you zoom in to the top you can see they are not aligned:



The root problem seems to be inaccurate end tangents on one of the curves - instead of having an end tangent going exactly along the z axis direction it is off at a slight angle:






So my first step to clean this up will be to go through and tune up all the curve points to be aligned to axis directions where they should be.

- Michael