pbdickey

I have an Apple Watch Ultra (not the Ultra 2), and indeed this is happening to me too.  I have spoken with Apple, and have been into the Genius Bar.  It is still not resolved and occurs what appears to be randomly.  A watch reboot temporarily fixes it.  When it happens the person I am speaking with is soft, I cannot understand what they are saying.  Even with the volume turned all the way up.  It renders the phone unusable.  The Genius at the Apple store told me she thinks a recent watch firmware update caused the issue to start happening, because she had seen it with other watches.  I told her that this was a key lifesaving issue for me when I am far from shore on my windsurfer and need to call for help if I am broken down.  She said the watch is not meant to take calls without a headset.  I told her it worked fine in the beginning, this is the whole reason I had purchased the watch, and it is not acceptable that Apple would degrade this functionality.