Pinned contacts disappear in Messages app on macOS. Is this some kind of AI by Apple?

Apple macOS Tahoe 26.1 Messages App pinned contacts disappearing without removing them.

I've noticed since I received my MacBook Pro M5 that my pinned contacts disappear without me removing them from my 9 pinned contacts/threads at the top.

Today, my sister was gone. I didn't remove her nor block her.

So is this some kind of automation that Apple has introduced or is it another glitch?