Hi Larry,

re:
> A minor mystery, most likely due to a lack of understanding on my part.

I think there's a bug somewhere in the automatic undo generation system when some intermediate objects are both created and deleted within the same command.

If you run into it again you might try using factory.calculate() instead of factory.commit(), like:

var object_list_result = factory.calculate();

The difference is that factory.calculate() creates "loose objects", meaning the objects have not been added into the geometry database automatically. If you're then using that geometry for internal construction and it's not supposed to be shown by itself to the user you don't need to have it added into the geometry database.

- Michael