In case others experiencing the issue find this thread, here's the reply I received from Airtable support: "It seems to be happening for other users as well, unfortunately. We have raised this issue internally and hopefully, a fix will be in order so...

I'm emailing support, but I'm adding a note that this is happening to me, too. Unfortunately, I can't connect Gmail or Outlook, so I'm stuck sending our members duplicate messages until this is resolved, but I wanted to amplify that it's a real bug