Thank you for the feedback @Richard_Robbins and sharing these observations you have made with us. The insight is appreciated!
If I am not mistaken the HP 1820-24G is a managed switch and we have seen a few issues crop up with these devices in the past ( Example: #1, #2, #3). I would recommend enabling flow control on the switch, as we have seen it help other users.
Additionally, you mentioned that when music stops playing to the Naim Uniti Atom without a “connection problem is being reported”. Can you confirm the exact error message being generated by the application.
-Eric