Hi Bodo-Lutz, I'm a little puzzled by the strange result but it seems to have something to do with these small line segments at the ends of the guide lines:



Try the attached version, here I removed those segments and stretched out the last control point of the next segments.

Also I noticed the 3 profiles were not closed curves, they have a slight gap here:





I closed those up by using Transform > Move on the upper point to move it down. I'll have to investigate the weird result, seems like a bug.

- Michael