Hi,
having some issues with curve union, they are closed curves, and are planar…any other reason why they might not be working?
File attached 
Thanks,
TomCurve.gh (81.4 KB)
May be try projecting the simplified curve on to a XY Planar srf. Then Plug the projected curve to Curve union.
Hi Bensonjtom,
The curve index number 32, which is a self-intersecting curve, is causing this problem. Region Union component doesn’t function properly with self-intersecting curves.
Best,
Tolga