As soon as the got my iPhone 16 pro a thing popped up in my FB messenger saying some of my chats were missing and asked me if I’d like to sync them; so of course thinking I lost messages I clicked and suddenly months worth of messages had been deleted from several contacts. Now I’m getting weird messages within my chats that messages were sent before my device was added to conversation! Like what does that even mean?!. I’ve logged out and back in, uninstalled and reinstalled both Facebook and FB Messenger, I even totally reset my new phone and nothing has helped. I was on the phone with Apple for an hour and although the agent was extremely kind and helpful he couldn’t fix it and told me Apple can’t do much about issues involving a third party app. But seriously I haven’t had this problem ever in over a decade with any of my iPhones causing glitches with messenger