Version/Environment (if relevant):
This affects Domino version 5.3.x to 5.6.x.
When trying to add a Central Configuration setting that already exists, you see the misleading error message:
Failed to create the setting. Please reload the page and try again.
This was a known issue where before saving a new key/value pair, MongoDB did not check if the key already existed and therefore did not produce the proper exception.
This issue is resolved in Domino version 5.7 where when trying to add a Central Config setting that already exists, you see the accurate error message:
Another setting already exists for this key.