Hi GpRanger,
You have tried some great troubleshooting steps that help rule out an issue with the iPhone.
If you are updated to iOS 16.3.1 and still have the issue, we recommend you use the steps here to reach out to Facebook support if this is only happening with their app: How to contact an app developer - Apple Support
1. Open the App Store on your iPhone or iPad.
2. Search for the app, then tap it. If you can't find it, tap the account button
or your photo at the top of the screen, tap Purchased, tap "Not on this [device]," then tap the app.
3. The app's product page appears. Scroll to the Ratings & Reviews section, then tap App Support. If you don't see App Support, make sure that you're signed in with the correct Apple ID.

Cheers!