Hi Michel,
Shell and Inset the calculation fails for this shape.
See image. Attached file.

Hi Zooen, it looks like the shell has generated all of the surfaces ok but has 2 trim boundaries messed up.

This can be repaired by untrimming the 2 messed up surface boundaries and retrimming them, that's what I did to get the attached finished result.

- Michael

Hi Michael,

>it looks like the shell has generated all of the surfaces ok but has 2 trim boundaries messed up.

I don't usually have a problem repairing solids for this kind of problem. It's mostly Inset that, at times, reacts strangely, or fails, when I repeat the same command several times on the same solid like this one because the values I've chosen don't suit me.
That said, thanks for looking into the problem.