SubD square curve extrusion bug


I’m new here and hope I’m in good section.
I see a bug with subd extrusion when I draw a square and exttude it.

Extrusion to a point : no problem
Extrusion alonga curve: no problem
Extrusion right: PROBLEM (see pict)

someone have an explication or methode do fix this ug?

thanks per adance.

esquisse extrusion subd bug extrrusion droite .3dm (159.1 KB)


Hi Laurent - I see that, thanks.