When did the relations panel change?

It might be from the last patch, but it could also be something I missed earlier.

In the past, when my sim interacted with some sim, that sim would move to the very top of the relation  panel. Contacts were sorted by latest interaction. But today I can't figure how they sort at all... When my sim interacts with a sim, that other sim seems to move a few icons, but not to the top. Sims listed top seems random, as my sim didn't even see them the past day (he did interact with at least 10 others who are not ranked any high.

So, what is the panel sorted by?