Resolution: When unloading a packaged map of a map that already exists, you are given the option to overwrite the existing one or create a copy. Both options will result in new GUID's being created for the diagrams that are unpackaged. This can be considered a safety featur, to ensure that you do not end up with duplicates of the same GUID's. This does mean that any external links (for example, URL's or SQL exports) will need to be updated with the new GUID's, in order to continue functioning correctly.