Certainly, that is not how the system is supposed to react. My guess would be some sort of wifi interference causing the Sonos controller to not properly communicate with the Sonos system on your speakers. Less likely, but not impossible, could be a simple duplicate IP address issue, which could be resolved by unplugging all Sonos devices from power, then rebooting your router. Make sure you wait a couple of minutes for the router to reload everything before you plug back in your Sonos devices.
Alternately, you could submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.
It definitely sounds like a network packet loss issue.
Also, removing the top room in the list is always more onerous because it’s the Group Coordinator (GC), responsible for fetching the stream and distributing it to the other group members. When a GC is removed a new GC must be appointed, causing all the live traffic flows to have to be rejigged.
Thank you both for your quick replies!
My wife uses the app on an Apple phone and the same thing occurs on hers.
But there’s definitely something wonky going on with my app. I hadn’t even posted about the other problem of sometimes when I open the Sonos app it says my phone isn’t on the same WiFi network as the system (it is) and wants me to reconnect. If I close and open a couple of times, or go through the reconnect steps it eventually does reconnect.
The WiFi network is solid, each speaker is fairly close to a wireless access point, and there shouldn’t be an IP conflict, but I can confirm. I didn’t see a way to find the IP of each speaker in the app, but I did see where the MAC address of each is shown and I can look at the router settings and match each MAC to the IP address. Will also try power cycling the speakers and the router as suggested along with the WAPs.
Hopefully something will work, and thanks again :)
But there’s definitely something wonky going on with my app. I hadn’t even posted about the other problem of sometimes when I open the Sonos app it says my phone isn’t on the same WiFi network as the system (it is) and wants me to reconnect. If I close and open a couple of times, or go through the reconnect steps it eventually does reconnect.
All symptoms of packets going astray.
Do also make sure that local device features such as VPNs or ‘WiFi Assist’ (on iPhone) aren’t getting in the way.
One other point: do you have a mesh WiFi, as well as a regular internet router?
The WiFi network is solid, each speaker is fairly close to a wireless access point
How close? Putting two radio transceivers too close together is actually detrimental to the performance of both. The usual guidance is to separate by at least 50cm, ideally 100cm.
I didn’t see a way to find the IP of each speaker in the app
The IPs are listed in the About section of Settings/System.
Thank you Ratty, that is SUCH helpful information!
None of the speakers are close to each other, they’re all in different rooms, the closest might be 15-20 feet apart.
I rarely use the VPN on my phone so it’s not running unless I connect it, and I have an Android phone.
I hadn’t gone into the Settings>System part of the app, IP addresses are all different (router uses DHCP but none have assigned leases to their MACs).
But…..yes, we have a mesh network. Non-Wi-Fi router with three wireless access points all with the same SSID (connected by ethernet) around the home. Just tested, and when next to one of the WAPs the app loads perfectly. Next to the others it either can’t find the system or only loads some of the speakers. I’d already restarted all of the WAPs but will do that again. I’ve not encountered anything that looks like packet loss with any other apps that I’m aware of, btut at least now I have a better sense of how to troubleshoot.
And other thing I’m now thinking…….added a Sonos amp to the system a couple of months ago, and while I’m not certain, that may be when the issue started, and one of the things that seems to happen when it doesn’t find the system after opening the app, it often says the amp needs to be re-added, even though it’s already connected (always shows when the app does load). No idea if related and I could be off on my timing, so could be a red herring or may be part of what’s happened.
Will keep troubleshooting…….
Thanks again 
Which model mesh are you using? Make sure that all of the SONOS players and the controllers are on the same subnet.
