Planar problem?

 From:  Ekenryd

Trying out Moi, but I have encountered a problem and I can´t see what is wrong.

I have two nearly identical curves, with the same amount of points as one is just a modified version of the first. I used trim points at some locations to be able to adjust parts of the curve more localized, then moved the edge-points to the same spot and pressed "join" to recreate a complete looped curve.

Yet, the modified version just don´t behave as the original one. I can do for example a loft, but it refuses to make planar and extrude from it. Have I stepped on a common problem here?

I´ve attached the file, I´d appreciate it if someone has a look at it.