Using Imported Grammar Rules

[ballcoach12]

I have a grammar that imports rules from another grammar. My entry rule looks like this:

entry TemplateLibraryModel:
    (library=TemplateLibrary    | 
        (
            globalBehaviors+=BehaviorDef*
        )
    )
;

The imported grammar appears to be valid, but the other grammar is showing errors in the Langium editor:

But, as you can see, the grammar is imported, and the BehaviorDef rule does exist and is valid:

I am unsure about what is causing this error. I used the editor's Quick Fix to insert the import statement, so I think the file is accessible. Is this a bug, or am I going about this import the wrong way?

** I will also note that the error in the editor goes away if I use BehaviorDef as a cross-reference instead of a grammar rule in the Xeta grammar file.

*** For reference, my overall goal here is to populate a global scope with BehaviorDef elements that are loaded from an external DSL file.

[ballcoach12]

Upon further review, this appears to be the same issue as #507.