I'm two months into this. Have posted quite a few times. Had BT issues since the start with my IP15P after trading up from IP11. Was on the phone with Apple several times, logs taken, troubleshooting, IOS updates, you name it. Banging my head against the wall with this. Going nuts!
On Monday I decided to call them again, just to follow up, since I haven't heard anything from Apple, and after I did the 17.2 upgrade (which didn't help). The support person read through my case and thought it was time for a new phone. He booked an appointment for me at the Apple Store for the same night. I went. What happened there was interesting. They set-up the replacement phone and transferred only the essentials, pics, contacts, etc. They did not do NFC transfer, like was done when I purchased the phone, this time only my info, no apps, came in from stored info on icloud. Apps would need to be manually installed. Reason being, as they told me, if something was contaminated in the old phone, they did not want to transfer it to the new phone.
It's two days now and I know it works flawlessly. Somehow, the original IP15 I purchased hiccuped after the NFC transfer and never worked properly. I'm not an expert here but it all makes sense to me now. Just want to pass this along.