We are saving similiar, dupe issues in a clustered environment.
I am able to track down the condition but have no fix yet.
When there are 2 URL and Msgs (The 2nd and 3rd unique arguments) that
are identical, we get duplicate entries sent to subscribers even though
the EmailAddress is different in both rows.
This function works fine as a standalone and there are only 2 rows
generated but each email address gets dupes for the same message.
If there is a single unique url/msg to an email, there are no dupes.
'en-US', EmailAddress, URL, Msg)