Try separating them as a stereo pair in the Sonos app and swapping the Fives. Then set them up as a stereo pair again.

Thank you so much for the suggestion, tried it, worked for 5 mins then the right channel (swapped the speakers) went out. If I remove the sub, works, adding the sub again disconnects it. 

Hi.  Please tell us a bit more about your network and Sonos set up.  Does your network involve any mesh satellites or wireless exttenders etc? Are any of your Sonos devices wired?

The two speakers are definitely stereo paired, not grouped?  They appear as a single “room” in the app?

Hi John, 

Sure, my setup is straight from the router wifi, no extenders and no mesh, the speakers are not wired. I went through the stereo pair set up (where it asks you to identify the chime for the left/right separation). 
 

They are vertical and when I remove the sub, it goes back to both channels (left/right) working just fine. 
 

i tried resetting every component, changed the network etc. But it doesn’t seem to be working, anytime the sub is added, the right channel disconnects. 
 

Let me know if I missed anything in that description! 
best,

JB

Hi.  Description was fine, but the problem baffling!  Is it possible for you to connect one speaker by Ethernet to your router, just as an experiment?  It could be a different speaker from the pair of Fives, or you cculd try the left speaker of the pair.

Give it a couple of minutes to reconfigure after this change.  Please then post back.

I assume you have a dual band router?  if so, are there separate SSIDs for 2.4GHz and 5GHz or just a single SSID?

Hi John,

It is indeed doing my head in! 

I tried the Ethernet wired on one speaker (both left and right) with an electrical grid internet extender to see if it could work, but did exactly the same thing. 
 

Separate SSIDs on the router, tried both bands! Reconnected the system twice to just test it out, right channel just goes as soon as the Sub is added. 
 

A bit out of ideas at this point. 
 

Best and thank you so much for taking the time. 
JB 

When you say you tried both bands, did you switch off one band and/or only have one SSID in Sonos?

(Tbh I don’t really think it is the bands but have to test).

Powerline adapters aren’t supported by Sonos, but that doesn’t mean they won’t work.  For our purposes, it is working if you go to About My System in the app you would see WM=0 next to your Fives rather than WM=1.

Otherwise, I suggest you run system diagnostics before and after adding the Sub and then call Sonos Support with the confirmation numbers.

I turned off the 5G band, kept only one then did the same the other way. Didn’t do anything. 
 

I’ll wait for tomorrow and get in touch with support, it’s infuriating and especially at the price point, but might be something I am doing right. 
 

best and thanks again for all the help. 
JB 

Refrain from Factory Reset without further consult. The reset will destroy diagnostic data that might have been useful.