Is MultiLineTraceForObjects working for "inner" Mesh?

Hi everyone!
I’m working on a StaticMesh generated by Triangles through the ProceduralMeshComponent class. It is a CT-Scan from an Embryo an it has some “inner” Meshes too. As you see on the picture I use a transparent material too see the interior. Now the user should be able to set pins to this regions.

I tried it with MultiTraceLineForObjects from the current position through the embryo but I only get the hit event on the current position. I draw the TraceLine and it definitely hits some inner meshes. But why aren’t there any hit results? If I flip the normals of the mesh I get hit results inside the mesh but not on the surface. This means there should be some results inside?