you have a bad foreign key without referred (Remote) table. You can use search functionality in advanced mode, object type foreign key (for your relational model) and add property (as search property) 'remote Table" or "Key object". Leave the text field empty and press "find" button.
If you get something in result then try to find it in the browser and to delete those bad foreign keys.
You also can use scripting to find those foreign keys as explained here Re: 184.108.40.2069: How to Verify and Fix a Possibly Corrupted Design?
You have 2 scripts there - 1) to report bad FKs, 2) to remove bad FKs
How did you get there?