Probably not an app problem.

Sounds more like WiFi interference, Sonos has a good FAQ on that if you can spell it correctly (I failed and had to come back here to get spellcheck’s help.) Don’t search for “WiFi interference” though as it won’t find it.

https://support.sonos.com/en-us/search?q=interference

https://support.sonos.com/en-us/article/reduce-wireless-interference

Thank you for your comments. My Sonos devices are wired. Should I reset my Sonos apps?

If they’re wired, I’d suspect IP address confusion on the part of your router. Unplug all your Sonos devices from power, then, while they are unplugged, reboot your router. Give the router a couple of minutes to recover before plugging back in your Sonos. 

If this process works, I’d recommend looking in to how to reserve IP addresses in your router, if a router has gotten in this state once, it likely can again

However, if you’re still experiencing the issue, I would recommend that you 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.

Thank you very much.

My ISP has sent me instructions on how to reserve IP for my Sonos.
IP should now be reserved for my Sonos. :-)