Both the alarm screen as well as the "enter share info" modal prompt for confirmation when navigating back regardless of whether any changes have been made in the first place, as well as when the "save" button was actually pressed right before.
This is independent of how back navigation is invoked (back button on modal, close button on modal, back swipe gesture).
Please make sure you are logged in with the Sonos Account that was used to create the system. That seems to be necessary now to get full control.
Then you should be ok using the correct account, because this just is shown to the system owner.
Did you try to reset the app from within its own setting and reconnect then with your existing system?
Sounds strange…
Any Ports blocked by firewall rules, ad blockers, pi-hole active etc.?
Did you try from a different device running Sonos app?
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