I've accidentally given a user the ownership of the db_owner schema (using the check box in the UI as below) and now I cannot:
- Transfer ownership to another user
- Drop the user from DB (though I can delete login in the SQL Server)
ALTER AUTHORIZATION ON SCHEMA::db_owner TO dbo
And while it completed successfully, the user still has ownership, and it's greyed out so I can't seem to do it in the UI either.
Found a solution:
In addition to Arron's answer, I realised that I'd run the above command in wrong DB (facepalm!). Once the DB had been corrected both the above SQL and the answer below worked.