Mailchimp for Sell Broken

Hello,

It is not possible to update audiences using the the Mailchimp for Sell app. Steps to reproduce: Select a smart list that contains multiple contacts that share the same email address > Add to audience > select a Mailchimp audience to import to > Add Contacts. The contacts are not added, instead it just hangs looking as if it is importing when infact it has not (HAR file shows it has stopped working). There is no feedback to the user that the import has failed.

Crucially, the legacy Mailchimp app worked fine in this scenario. But the legacy Mailchimp app has recently been discontinued earlier this month. So it is no longer posisble to update audiences in Mailchimp.  The new app needs to be able to skip over duplicate email addresses like the legacy app did.