Bluetooth connectivity issue with the iPhone 15 Pro

I am having a Bluetooth connectivity issue with the Iphone 15 Pro, Oticon hearing aids. and my 2016 Audi Q5. The phone will connect to the car, and sometimes route an incoming or outgoing call through the car speakers like it should. Then randomly, a call (both incoming and outgoing) will be routed through the hearing aids instead of the car's speakers. When this happens, the car says the phone is connected to Bluetooth.

I have rebooted the phone, reset network settings on the phone, deleted and reinstalled the phone to the car, deleted and reinstalled the hearing aids, turned Bluetooth off and on again and nothing seems to work. The Bluetooth connection in the car seems fine if I don't wear my hearing aids.

Prior to upgrading to the iPhone 15 Pro, my iPhone 11 handled the simultaneous phone and hearing aid connections flawlessly with the same hearing aids. My gut tells me this is a software issue with the phone.

I would appreciate anyone's suggestions on what what else I might try. I would also appreciate it if the Apple software developers would help solve this issue in a future IOS update.

[Re-Titled by Moderator]