Tagging e-mails sometimes sent twice

Hi @audrey, while looking into a query to get yesterday's tagging numbers, I noticed that occasionally the system sends two e-mails for the same manuscript to Molecular Connections at the same time to notify them of a new package.

I don't see that it will cause any problems for the taggers, because the package is the same, but it would be good to avoid this.

An example is EMS83390 sent to the taggers on 2019-06-17 at 10:18 BST. There's only one entry for the status changing to tagging in the audit_log, but two e-mails were sent. I'm afraid I don't have a reason (or even a guess) for why this happened.