The object "Object001" in provided scene has inverted normals (polygons are facing downwards). Flipping normals will fix that.
Regarding Loft objects: We're able to reproduce problems when using a Loft object as a Surface for Forest's distribution - it occurs within the 3ds max core when the bounding box info required by our plug-in can't be accessed. Unfortunately, from our plug-in we don't have any influence over it.
As a workaround, please apply the Edit Poly
) modifier over such object to avoid this unwanted behaviour.
I would encourage you to contact directly Autodesk
regarding this bug. Once they'll see, there is a real demand from their users, they'll prioritize that. I'm afraid we can't do much more in this case. Thanks for your comprehension.