@Eileenmcnaughton I'm moving this to chaos for now, let me know if it's more visible for you in an upcoming sprint.

From what I can tell here, all three examples are contacts that were merged multiple times and had two contacts at the time they received the emails of concern.

Part of the issue here is that there is small bug that can result in Mailing Events being recorded on deleted contacts after a merge, see T404404.

@SHust it looks like your case in the May 29 comment is a case of multiple duplicates. Email 2 was presumably sent to CID 34989476 which had the same email and presumably the old name. That CID was only deduped into the current contact about 10 days after the mailing had been sent.

@NNgu-WMF For CID 42510970, it looks like the most likely explanation here is that Email 2 and Email 3 were sent to CID 20534282. Then the question is why those Mailing Events weren't visible on that contact at the time. Unfortunately, I don't think we have logs that are detailed enough to answer that question now that the contacts have been deduped - but we can certainly look at it again if it comes up with another contact.

For CID 26416503, their deduped deleted contact CID 63985888 has the Email 3 Mailing Events. This is because of the bug mentioned above.

So I think since these are all cases of duplicate contacts being sent the emails that resolves the issue as well as we can.