If the isocurves do not correspondent with the triaxial deformation then you need to find the minimum boundingbox and create the section curves based on that box (see attached ). Ellipsoid.3dm (131.4 KB)
I also don’t know what the bug-fix is about but I found that the IsEllipse check is pretty tolerant. However, once you have the minimum bounding box you can scale the sections to be quadratic and check if these are circles.
The tricky part is to find the minimum boundingbox. I made something for that
but it is not ready to be released.