So yeah the variable radius fillet part is also problematic for offset/shell because it's not smooth to its adjacent surfaces:





Was that part maybe made by patching in with a network surface instead of from a fillet? Anyway it's not smooth there and that adds a lot of complexity to doing surface offsetting because only surfaces that are smooth to each other will produce offsets that naturally touch each other. Offset surfaces at sharp edges will have gaps between the offsets.

So one thing you could do would be to leave out that transitional fillet piece from the individual surface offsetting described above and patch it in doing Network on the offset pieces instead.

- Michael