Metabase upgrades may affect user-written grants and reports against the Connect CDC metabase. You must re-apply grants after metabase upgrade. Also, some tables may not exist or their structures may change between releases, which may cause customer-written reports to fail.
You should remove the metabase before you remove a server from your model, for clean up purposes.
To do a clean installation because of problems with the existing installation, remove the entire metabase (including the user and login created for the owner of the metabase objects). See Remove a metabase for more information.