Since a couple of updates back (maybe 2 or 3) I've experienced that the sonons app -around twice a week- just doesn't find the sonos system anymore. My WiFi is up, I have internet, everything else works (even the TV works and can use Sonos) but the app just won't find my sonos system. Workaround is to plug out and in my router and then the sonos app will work again. But it's highly annoying to reset your router twice a week just because one app "hangs itself" - or whatever the case may be. My internet and wifi are both fine. I work on my wifi, my PS4 is on my wifi, everything works, except sonos app, that doesn't find the system.
And this never happened before in older releases. So this is meant as a feedback on the app and I hope you get an idea for fixes.