I’ve noticed this today during a session. It’s really weird. The edge to match to, kind of automatically chains the selection with even prompting ChainEdges. But even more weirdly, it forces me into a corner and then doesn’t even do the match.
Even weirder? It seems to be on a time delay. If I select the edge to match to too soon, it does the odd chain. If I give Rhino a second for a breather, it correctly selects just one surface edge.