Message Oracle ORA-54509 - solid not attached to composite solid

ERRORsolid not attached to composite solid
CAUSETo connect solids in a composite solid geometry, at least one of the faces of a solid must be shared (fully or partially) with only another solid. However, at least one of the faces in this composite solid was not shared by exactly two solids only.
ACTIONEnsure that at least one face in a composite solid is shared by exactly two solids.