Take a look at the attached - The last of the geometries would be my expected outcome, but Railrevolve displaces the axis and Sweep1 produces weird artifacts at the bottom. Am I totally wrong in considering this a bug?
Hi Jakob - this has to do with the shape curve locating a closest point on the rail - to know where to start/end the surface. If you set up the curves like this, so there is no ambiguity, it should work:
