Can't seem to create rounded shape

 From:  NightCabbage
Hi all

I'm having trouble making this shape with the Network tool.

It gets it almost right, but for some reason it buldges it outside the shape in certain places...

(right side - note the pinching towards the corner)

(bottom left - see how the surface goes outside the curve I specified)

Any ideas? I know there would be many other ways to make this shape, but I'm a big fan of the Network tool, and want to know why it's now working as I expect.
(for example, I can get my perfect shape using Revolve on the top round curve)