Hi FDP,

> Is it possible that this is just an error in the way that MoI reports whether an object is solid or not?

Yeah sort of in a way - basically MoI will label an object as a solid if it has all edges joined between 2 surfaces (or joined across the same surface as a seam edge on a closed surface).

There are various kinds of ways that objects can be malformed that will still fit that basic criteria like with trim boundaries that have little self-intersecting loops, surfaces that intersect themselves, or pieces of the model sticking through each other, or other kinds of malformed boundaries. This particular one with the boundary actually located completely off the surface is not very common.

Unfortunately it would be extremely time consuming for MoI to try and do an intensive in depth analysis of the object to determine these kinds of malformations.

- Michael