Net extrusion and Surface Split with Brep BBx problem when cutting

Hi I am having some trouble trying to create a net curve surface and then extrude it and cut it with a brep inside the geometry but somehow the net extrusion only works with a rectangular shape like in this image.

Once I do another shape or I want the net curve to take the shape or adapt to another surface it appears like this, it looks very messy.

I also tried with pufferfish and the net component but the same problem happens I cant manage to adapt it to another surface that’s not a square or rectangle.
Also as you see in both images once the brep cuts it doesn’t do it very clean, so there are parts of the extrusion that should not appear once the brep has been split.
I attach the gh definition and the 3d file.
def test.3dm (124.4 KB) (74.8 KB)