I tried that, but it didn’t work for me. Still getting the Spirograph after using ModifyRadius on a Box-edited circle. In object properties, it is still a “Nurbs circle” even after the modifyradius operation.
I also tried Scale2D on a pristine real circle (Object properties: Circle), but that too led GearGen astray – the object had been transformed into a “Nurbs circle”, same as what happens with BoxEdit.
But what Mitch says is true about SimplifyCrv – that command changes a “Nurbs circle” back into a “circle”, and GearGen works again on that object. I think he’s put his finger on the solution here. If you build that into your script, it looks like it will solve the problem.