At the moment is not possible to merge contacts that are currently enrolled in a sequence.
This is because merging a contact that is in a sequence can trigger sending duplicate emails or unenrollment from a sequence that can cause unexpected issues.
What I suggest is to wait for the contact to complete the sequence, and after completing, you should be able to merge the contacts.
I realize this is super old BUT: It would be really helpful if on the "manage duplicate records" menu they allowed for a "in sequence now" column. Currently I have to click into every single one to see which is in a sequence which is super time-consuming. If I just could see that they were in a sequence from that first menu I could skip them quickly and move to clean-up the ones that aren't.
That's a great idea. I would recommend you create it in our ideas forum and commenting on your use case, so you're automatically subscribed to the idea. You'll receive notifications when our product team makes a status update to the idea.
The more people vote for the idea, more chances will have to be implemented in the future.
At the moment is not possible to merge contacts that are currently enrolled in a sequence.
This is because merging a contact that is in a sequence can trigger sending duplicate emails or unenrollment from a sequence that can cause unexpected issues.
What I suggest is to wait for the contact to complete the sequence, and after completing, you should be able to merge the contacts.