I made a similar post last year with the same problem. It has reappeared, this time for May.
As you can see above, including the first (or final) day of May removes all "Who played the most" info from the entire month (this happens with longer ranges as well, I tried with June included as well as overall, and May's stats aren't included in those).
You solved it last time, so I'm just letting you know in case you're unaware that it's back.
Thanks in advance,