Hi Michael, when MoI saves out to 3DM it involves a type of translation from the geometry library's own native data structures into the 3DM ones. This can potentially change a few kinds of things like the order that things might be listed. Under normal circumstances these things are not really supposed to make any difference but it is possible for that to have some impact on particularly sensitive operations.

One thing you might try in general is to not put on the smaller fillets until after you've done the shell, especially the corner juncture areas can be particularly difficult for the shelling mechanism to handle, it has to try and construct offsets of all those pieces.

It's unfortunately quite difficult to give you a specific reason why it worked for you before and not now - most likely there is some kind of bug involved but it will be pretty difficult to figure out exactly what.

It does not look to me like you've done anything wrong at all, other than maybe if you know you want to shell don't put on the smaller fillets until after the shell instead of having them before the shell. Although just to make life interesting there are also other particular situations where putting on a fillet before can actually help, if it helps to avoid the kind of offset situation where one vertex in the base surface would need to diverge into more than one in the generated offset, that's the particular kind of situation that the offset mechanism in the geometry library does not handle currently.

Basically shelling is not a very strong area of the geometry library that MoI uses, it can be good to have ViaCAD to use along with MoI to do some kinds of shells that MoI can't figure out.

- Michael