So I’ve been digging in, most of the morning, trying to sort out some confusion in the example you provided me. As I mentioned earlier, right out of the gate, something caught my eye in the campaign history of your contact. I was not seeing the process to Apply Tag in the contact’s campaign history. I tested by adding a test record with a custom date, and dropped them into the sequence, and everything laid out perfectly, Email, followed by apply tag (the STOP tag)
As I dug deeper into other recent contacts in the campaign, I noticed a trend, that led me back to something going wrong somewhere around the 11th of October. I found that there was a publish done this day. I am not sure what was changed/edited and then published, but it appears something may have happened during the publish that affected the existing contacts in this sequence, as I ran across a few that looked just like your example.
My next idea would be to make a non-relevant change to this campaign to trigger the ability to publish again, as this should take the existing contacts and ‘reschedule’ the missing process(es). Now, I don’t want to just publish your campaign for you, because if this works the way that it should, some contacts may shift around, as the contacts that did not get out of the sequence should pop back into active to receive this stop tag that they missed.
This is one of the stranger things that I have seen, as this campaign is pretty cut and dry, but I am seeing Add Tag processes missing from Recent Campaign History and Upcoming Campaign Elements for contacts existing contacts in this sequence.
This is one of the stranger ones I have seen, as there is usually an off the top explanation on these types of issues (tag was applied in error, prior to getting into a sequence, issue with way a looping campaign is set up, etc) but none of this appeared to be the case with your current setup.
To continue looking into this, a re-publish would be recommended, as I am finding the issue may be surrounding an issue with the last publish of this campaign on Oct 11th.