I decided to put frustration to rest and do some simpler illustrations.
I had what I thought was a simple offsetsrf that I was doing outward at 25# (=25/40). I failed to create a closed surface.
So I copied the polysrf to the attached file. Then I duplicated (to the left) so that I would have a before and after example. Then I do offsetsrf on the the left side at 25/40"----and it works. I was scratching my head until it bled. Then I found that original (at the right fails).
Why would offsetsrf work when for a copy in a different position but not for the original?
Problem Offsetsrf.3dm.zip (107.4 KB)