GeometryFile node for importing spread of small objects, maybe that's what causing the problem....
There is bug with assimp nodes, but that's more of 3d exporter problems, bug called 0 vertex subset, appears when 4d exporter creates some sort of dummy object, There will be an error on shader pin tho...
I can suggest you to use scene assimp instead, there is also node called sceneexplorer(assimp) will show you what's inside of your file
SceneLoader (DX11.Geometry Assimp).v4p (9.1 KB)
this module proved to be minimum amount of nodes to work with 3d files
also you can upload one of your meshes to check them out
there is this thing for windows if you can test model with it http://www.open3mod.com/
also when you are using geometry file, there are no predefined transform so your mesh could be 100000 bigger then what cha see, also check of you don't have troubles with texture coordinates (uv)