I think this link speaks for itself. Review items in the Late Answers queue always used to require only one user to be completed, and the only way you'd see more than one reviewer on the same review item was if two people were completing it at the same time. The review queues on that item are hours apart, and when I logged in to Puzzling this morning, I saw the red dot in the review queue dropdown indicating that something was still outstanding to be reviewed.
Weirdly, I don't see the same thing happening at Sci-Fi and Fantasy - all recent review items in Late Answers have only been reviewed once (link will work only for high-rep SFF users). I don't have full review tools privileges on many other active sites to check their review queue history, but it's unlikely that such a bug has affected only one site (that would be puzzling indeed), so I'm posting here on main meta to ask what's up.
Why are (some) Late Answers review items suddenly requiring more than one user to be completed?