Simple shape will not shell

Problem 100.3dm (741.9 KB)

In the attached, I am trying to shell to around 0.04" while removing the face indicated by the four short lines.

I keep getting a non-solid from the shell.

How can I get this to shell?

Yeah - your file tolerance is .01 and the offset is only 4x this - not a very good situation. Setting the file tolerance to .001 makes a better if not perfect shell, not too hard to repair. OffsetSrf also works at .001 but not at .01 tol.
Problem 100_PG.3dm (767.9 KB)

-Pascal

I was working in a file with lower tolerance and copied to the default. I don’t get a shell with .0001, .00001, or .00001 tolerance.