Business Architect: relationship not carrying over to all diagram containing the two entities

In Business Architect 17.0, I created what was effectively a "submodel" diagram that contained just a small subject of Business Entities for a portion of a Conceptual Model. We created another diagram with all the Business Entities and relationships (let's term it the "complete diagram"). Some of the relationships that were created in the "complete diagram" do not display in the "submodel" even though the associated Business Entities are present.

Similarly, a new relationship was created in the "submodel" diagram, however the "complete diagram" doesn't display that relationship even though the two Business Entities are already present in that diagram.

Is this a known issue or do I need to submit a Case?

Is there a workaround?