This error has been around since 2019. When you have a table you're 'working on' and rename the table (even with no FK constraints or external connected references), when you refactor, the system breaks down and doesn't allow you to save the table, requiring exit without saving. When you save and exit the .dbd, the table is gone from the diagram, and you must manually drag and drop the new (renamed) table from the table list to re-add it to the diagram.
In the below example, all I did was rename the table from system_log_error_notification to system_log_error_review and refactored.
