Email notifications possibly sent out before whole transaction is complete
In some cases email notifications might be sent out for changes that will subsequently be rolled back.
The case we observed was with 2 related issues. The update was to close the primary issue, which caused the related issue to be closed too. The primary update failed because of a stale object error (the primary issue had been updated by another user between when the first user opened the issue page and he tried saving it), this also rolled back closing the related issue.
Unfortunately the email notifications for the closing of the related issue had already been sent out, and users were confused to have received a notification about the closing of the issue, but not seeing the issue closed nor seeing the change in the journals.