I’m having the exact same problems on my iPhone XS. I’m in the Las Vegas area and it is unrelated to my case, Bluetooth, location, signal strength, etc. only “fix” is to restart the phone, which will work for a day maybe. I have tried all the same troubleshooting techniques and all software is up to date. My wife’s iPhone Xs has same problems. As mentioned above, it seems obvious there is a device-specific conflict. Please update us when a solution has been determined.