I'm struggling to get Xperia 1V to pass call audio and stream music to my hearing aids
(Oticon mini rite)

The phone can do this - I've had it working after a series of pairing/unpairing/repairing. But I can't say what I did to get it working other than turn it on & off several times.
I then lost the ability when I'd connected by USB-C to a different sound output, my car, which was recognised as a headset.
The phone didn't revert to the previous working audio streaming setup after I disconnected from the car.

But it still detects and automatically connects to my hearing aids, and defaults calls to Bluetooth, which I then can't hear.
I've just switched from a Google Pixel, where the sound worked faultlessly, so stock Android 14 doesn't have these issues.

Any ideas on how to fix this?

What can I do to set