Hi @nicolas.lefevre
Without a 3D file to look at, it’s really hard to see exactly what you are doing, but…
For Sweep2, you should set the “Curve options” to “Do not change cross section”, especially when you have cross sections that are polycurves with both straight and curved segmensts, like you do. If the preview looks weird, it’s probably because you curves are not completely similar in structure, and this might be corrected by using “Add slash” to specify where the cross sections are meant to align.
But I think that maybe you are better off creating the three sides as separate surfaces and then using filletedge to create the rounded corners, but again: It’s much easier to help, if there’s an actual 3D file to look at.
HTH, Jakob