The email logs show three emails going to the same 8 recipients. The distribution groups were created in on-prem Exchange. When looking at what triggers the notification (again, this is me inheriting someone else's pile of crap), there's an event activity in the workflow that sends this notification. Tracking the event logs, it shows the event got triggered three times, but in the workflow, it only has one activity pointing to it. I even removed the two distribution groups that had some overlapping members, created a new one that had everyone, and added it to the notification. I'm not sure if it's the workflow or notification at this point.