I've overcome my script problem with leaving extra circle and line geometry upon Cancel in the middle of the script.

Attempting to objectpicker select the Face and generate curves for the base/top/slantseam with Copy factory, was interfering with objectpicker selecting the curves/edges.
Why this has been so is still a mystery. The previous .clone code worked OK, but had the extra curve problem upon Cancel.

But by removing all of the objectpicker Select Face code, and not generating .clones or copies of edges, by removing that code, a mere click on the appropriate face, and then selecting the edges works just fine. It is too late to clean up the reduced size code tonight...

- Brian