The Separate factory only produces output for curves which can be separated.

The separate node needs to be altered, to pass on closed curves which are made up of only one segment, (including elementary circles and ellipses, etc.)
Closed polygons should be separated for the conformal mapping. (and stereo project?)
So test for isClosed, and also check for crv.getSubObjects().length ==1.

Is there a test to tell when a curve can be separated?
EDIT: Michaels previous answer from: https://moi3d.com/forum/index.php?webtag=MOI&msg=8818.8
"The segments of a curve are returned by the getSubObjects() method which is available on every object type in MoI. A curve always has at least one segment. To see if it's made up of multiple segments you could do crv.getSubObjects().length > 1."

- Brian