It may just be a case that the controller is not ‘discovering’ the Sub on the network occasionally, even though it is present and is still working okay. Is this an iOS controller by the way?… if so, maybe see if switching off ‘Private Address’ in the iDevice network settings solves the issue for you. If it happens again also see if toggling off/on the WiFi network on the controller mobile device resolves the reporting issue.

Thanks Ken, it is iOS controller. Please explain how to turn off Private Address in iddevice network?  I’m not technical in any way, sorry. 

I’ll explain what you need to do (below), it’s quite easy, but I would first check to see if it is definitely a ‘reporting’ issue. So when it next happens and the speaker/sub drops out - first submit a Sonos diagnostic report just for good measure (make a note of it’s reference number) and then goto your iPhones settings and toggle off your WiFi connection.

Close the Sonos App (slide off screen completely).

Then switch the iPhone’s WiFi back on and reopen the Sonos App to see if the speaker/sub has returned. If so, I would also do another Sonos diagnostic report here too. (Make a note of it’s reference number too), it may help to hang onto those references.

If the Sub returns when the WiFi is toggled off/on, then perhaps see if switching off iOS’s ‘Private Address’ feature fixes the matter and stops the issue from happening again…

Switching off ‘Private Address’.

Goto the Settings > Wi-Fi on your iPhone or iPad. Locate the Wi-Fi network in use that you want to change this option for—it’ll be at the top of the screen if you’re currently connected to it. Tap the “i” icon at the right side of the Wi-Fi network name. Look for the toggle on/off switch next to ‘Private Address’ and set it to ‘off’. You’ll likely be prompted to rejoin the network if you’re already connected. Tap “Rejoin” and your iPhone or iPad will rejoin with its normal MAC address.

See if that simply change sorts the matter. If not, then post your gathered diagnostic reports back here and speak/chat to Sonos Support Staff via this link:

https://support.sonos.com/s/contact

HTH

Thanks Ken, seems to be fine now after your advice. 

Thanks for the feedback. These things can just be a ‘reporting’ issue between Controller and the speaker, but often ‘all is well’ in the actual bonded setup on the Network. I have seen it too occasionally and sometimes a switch off/on of the iDevice Network connection will resolve the matter. Anyhow glad to hear that it’s all good so far.