FBX Export parented objects are missing

I have a Problem with the 7.4 binary FBX Export from blender that when I Import my FBX File in Unity or Substance that some objects what are parented are missing.

When I unparent them and Export it all is fine.

Also when I use the ASCII 6.1 FBX Export all is fine.

What I also done so far recalculate normals & Apply transform, Rotation & Scale to the Objects where i have Problems with.

I created a little Testscene and could definitely reproduce this behavior in the Screenshot below you can see the small “Testscene” that I have done. When I now Export this then the small Cube is not shown in Unity or Substance.

Did anybody has an idea what is going on here?