ios 18.1 message filtering displaying incorrectly

iPhone 12 Pro Max recently upgraded to iOS 18.1. I have my messages set to filter unknown messages. This previously worked well. Now, if I'm reviewing "known" messages and exit (or just leave) the app, when I return the header says "messages", rather than "known" (as I left it) and all my messages, known AND unknown are displayed. (this may be happening after I receive an "unknown" message, not sure).