Solid Union co planar / co incident?

Hi guys,

I'm trying to solid union some geometry produced by sweeps...the sweeps all take the same profile from the a single starting plane....for some reason the solid union is reading "empty set." 

I got it work using a whole bunch of lofted profiles which produces planar srfs...however I would ideally prefer one smooth srf.

Any idea?

I've attached the script.

Thanks!