Alexa/Echo calls ringing on other devices after a call is answered

[rcgentry]

I have had a number of Echo devices for some time.  My partner and I call each other (we don’t currently live together) on Echo Show 5s.  This has always worked fine until about 4 weeks ago, when although the calls themselves are successful, our other Echo devices (including iPads/iPhones) continue to ‘ring’ after the Show 5s have been answered.  The other devices show the calls as being from “unknown”.  This issue appears in either direction i.e. irrespective of which of us makes the original call.  Any suggestions please?