archiving not removing patient from mailchimp

I want to report an unusual error that we ran into between Front Desk and Mailchimp. In a recent email campaign, an email was sent in error by Mailchimp to a deceased patients email address that we had archived 8 months ago in Front Desk (I did sync Front Desk with Mail Chimp before sending the campaign). I have investigated what happened from our end, and found that the email address that we sent to was used for both the archived patient and her daughter, who is still a current patient. So it seems that we had previously linked the email address to the archived patient, and that this link was not reverted to the daughter at the time of archiving. This lead to some embarrassment on our end as the daughter reported the problem to us and I suspect some upset with the daughter. 

I hope this makes sense and that a fix can be found so this does not happen again.