Hi niko, thanks for posting that - I think I may know what could be happening there, I think it is an issue of Blend using the edges directly and being sensitive to differences in control point spacing on the edge curves.

It's similar to an issue that used to be in MoI's 2-rail sweep command as well until a couple of betas ago. I think that probably the same fix for sweep applied here should solve it in Blend as well, I'll see.

- Michael