A Lead enrolled in a Sequence has replied to my email. That contact was unenrolled automatically and I replied to him. But the issue is as follows. The contact was sent the following email from the sequence and re-enrolled in the sequence. The Activity field does not indicate that the contact was re-enrolled.
Have you checked out the sequence enrollment history (more info in this HubSpot Knowledge Base article)? That should give you more insight into the sequence actions that have fired for specific contacts.
Also, can the email in question be sent only from that one sequence? Or is there another sequence/automation that could have sent that email?
I haven’t heard of an issue like this before, so your next best bet would be to open a ticket with HubSpot Support. Just be ready to share the links to the specific contact(s) and sequence(s) you’re working with!
I would recommend following @jolle’s advice on contacting HubSpot Technical Support. They will be able to provide real-time assistance for this matter, where you are able to share screenshots and links to the affected contacts in your account.