Sonos Port: Wired connection but still music is interrupted

The iPad is okay? Is it on a different WiFi band to the iPhone? 

Nope. That's the strange thing
Both are of the same wifi (ssid) and both are in the 5ghz band
When i open the app on the iPhone today, all seems to be fine again. So also the iPhone shows the kitchen....

Disconnected the kitchen one (L) from power for 30 sec and then plugged it back in. Both kitchen ones are now back on 2.4ghz and the problem seems resolved.

Could this have been the RCA? If both Ones are not on the same band (even though they're on the same SSID) that the app states that 'keuken'/kitchen was no longer properly configured?

It sounds like it. The system would much prefer the stereo pair to be on the same channel, as one can then communicate directly with the other rather than having to go via the router.

Maybe Sonos needs to do some additional work to address all this. Connection to 5GHz WiFi is a relatively new option, so perhaps this is a teething issue.

One option you could consider is to split your router bands, naming the 2.4GHz and 5GHz differently. Add both to your Sonos system and see if that makes any difference. 

I've already got a guest network available on my router. I believe this then also would do the trick
If i put kitchen on guest network ssid and the rest on the regular network, will the app, who'll be on the regular ssid, still be able to see the kitchen when this is on a different ssid?

You can't use a guest network. The whole point of a guest SSID is that it's isolated from the main network. 

It'll usually be on a different IP subnet, and/or have wireless client isolation to prevent devices from seeing one another. 

Understood. So eventhough the iPHONE app would be on SSID 1, it is still able to control the SONOS devices which are on SSID 2?

If SSID1 and SSID2 are the regular 2.4GHz & 5GHz WiFis (not the guest one) it should work fine, as everything will be on the same IP subnet. There are a few routers which can cause trouble but they’re pretty rare.

As I say, the guest network is useless for Sonos.

Understood. I misread the CAN'T use. My bad. Thanks for re claryfiyng. 

It's getting stranger and stranger…

The line in (ingangsbron) is not found, but music is playing...as to be seen with the 3 vertical icons on the right

So I'm playing vinyl via the port (line in), even though the systems doesn't recognize the "draaitafel” (turn table)

So I'm completely lost now.

How can I play music via a device (port) which officially isn't know to the sonos app?

Connecting to wifi is getting worse and worse by the day. (The drop outs are almost gone, but operating the sonos via the app is almost undoable) (Randomly devices are disappearing as they're no longer seem to be connected/detected)