iPhone 11 Pro Max- no text sound when bluetooth on. No devices paired with phone.

Still looking for a solution to this. I've been struggling with it for a few years.

When bluetooth is on, I will intermittently not get text notification sounds. I've deleted (forget this device)- all bluetooth devices. Even though there are no paired bluetooth devices (nothing listed on the bluetooth page), if bluetooth is on, I get the notification on the screen, but no sound (intermittently). It happens with various contacts.

I've reset my phone, upgraded IOS etc.

If I turn bluetooth off, all the notifications happen as they should, every time.