Civil 3D custom subassemblies created with previous versions of SAC may not work as expected when imported to later C3D versions

Custom subassemblies created with previous versions of SAC may not work as expected when imported to new c3d versions (although if already in a drawing of a previous c3d version will work fine when opened with later version!).
I met such a case. All previous version subassemblies worked fine except one! Worked fine when opening a previous version dwg file already containing it. But did not work if imported from scratch to a later C3D version!