Here is a copy of a recent email I received from Apple
We have released numerous updates to address this issue which has resolved it for some customers. As stated before your Phonak hearing aids are not a Made for iPhone device like other models that are supported by our company. I have provided a list of made for iPhone models that are supported by Apple. I can gather logs and submit the issue up to our engineers as done in the past. Per Phonaks website it does state they support compatibility with your phone models. I would recommend reaching out to Phonak as they are the ones stating compatibility not Apple. Let me know a good time I can call you to collect logs if you would like to proceed.
I had asked Apple if they were going to do anything and the above was my answer. I have KS9’s but have the same issue as Marvels.
I had been communicating with Apple support for months and this the response when pressed for a resolution.