Hi Paolo, right now sweep in MoI tends to be sensitive to uneven spacing of the rail's control points. The profile's has some control points closer together in that area, that makes the sweep be kind of bunched together in that area as well.

I am planning on fixing this up in v2 when I get a chance to do some work on sweep, I'll use your file as another example of the problem to work on, thanks for posting it!

- Michael