Hi Linker, thanks for the bug report and example model.

It appears to be going wrong somewhere down in the guts of the sheller, so it may be a little while before I'm able to drill in there and figure out what has gone wrong with this one. I've added this to a stack of geometry library bugs to look at in a while.

I'm sure you have already figured this out, but to finish this particular model you can shell each part individually and then boolean union them together.

Getting these example models is really a big help, thank you!

- Michael