In the attached I have a solid (center) that I had shelled many times and suddenly it failed to create a solid (left). It turned out that I had intended to shell at 3/4" and had shelled at 1/2". Then I shelled at 3/4" of an inch (left) and it worked as it had in the past.
It seemed odd to me that it would shell at 3/4" but not 1/2" so I share.
Problem Shell.3dm.zip (324.7 KB)