I apologize for apparently inadvertently maligning the software, and will endeavor to be more precise in my statements.
Clarification: This offset technique did not work for me, as I attempted to use it, on my own computer, using a recently purchased copy of VCarve software, on a new MacBook running Windows via Parallel. The test file that I posted is the one used in the second try, which resulted in an error on my computer.
All other features of the VCarve program seem to work fine on my own setup, as per examples seen here on the forum. I readily admit that this technique apparently works fine for other people. I also readily admit that I'm -very probably- doing something incorrectly, particularly as I'm a new purchaser of this software product.