In the 'normal' discussion forums there are year-long threads discussing this problem which still persist in the iOS 17.3 developer beta: with APP2 paired with Xs or Xs Max there is a delay of 30 seconds when answering a call before speaker and mic in the APP2 come to life. Most people trying to reach me usually give up before this half-minute delay have expired. They usually call back right away and this time the APP2 work immediately. Factory reset of both phone and APP2 makes no difference. For reference here is one thread opened in January 2023 with 571 marks as 'Me Too'. Until the problem is resolved I will use my APP2 with my old Nokia 7 Plus where phone calls are handled flawlessly.