Archiforma Tube using 3D Polyline

[Anonymous]

Hey forum,
I've been trying to create a sloped concrete construction as the ending of a slab/roof (see pic.1) The slab/roof has two slopes, so I created a 3d polyline using archiforma and then used tube extrude with the profile I needed, at a first glance everything seemed OK and I was but when I made some sections to check the heghts, I became because I saw that for some reason the original shape has been altered,as you can see (pic2), I get different profiles in every section and not even one is planar.
Pic3 is just a 3d render to give you a nicer view of what I want to do
Has anyone encountered something similar?
Cheers