Thank you Michael for the explanation.

Trimming and blending cured the situation.
The parametric equations yielded results which may be very slightly non-symmetric, but not enough to see without zooming way way in.
I switched to Curve factory rather than InterpCurve factory.
Maybe the parametric equations could use 1/3 the value of theta angle, rather than 2PI.
Just playing around...
I'll post a .png, as soon as I remember the image service name :-) (imbbox)
Just did a 4 leaf clover script. It has crossing curve lines with narrow separation. Trims and blends fixed it up. May post it tomorrow.

- Brian

https://imgbox.com/yJnRkPAo