Ugly extrusion ! (WHY ?)

Greetings !

I just noticed that a very simple extrusion in my model generates unsmooth faces.

Profile:

Resulting extrusion:

I tried with the "Image Quality" settings to the roof without any improvements.

Funny thing is that if i loft from this ugly facet to another profile i get a perfectly shaped and smooth solid.

What am i doing wrong ?

SolidworksParts And Features