It’s odd, I don’t experience this ‘always fail’ state. While occasionally, I have difficulties with the update timing out too early, it certainly doesn’t fail. Especially if I just wait an extra half hour, to allow the update to ‘finish’ on the reported errant speakers. 

It sounds like you’ve tried many of the things I’d recommend, without success. Have you called Sonos Support directly to discuss it?

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 network and Sonos system.

​@bdestroys 

Have you ever tried updating using the Windows or Mac app, downloadable from the Sonos website? It has worked so many times for people whose phone updates don’t work. 

Why not let the system do the update at night automatically? That way it has the time to get it right without bothering you.

Yup. Have exactly the same problem and have tried ALL the suggestions from SONOS and community including using the app on Mac. Nothing works. Every time there is an update and it forces you to do it or you can’t use the app, if fails. 
 

I have two Sonos speakers as surrounds on wifi and my playbar is wired to the network. 
 

either Sonos need to fix this or STOP FORCING PROPLE to update their system when set to OFF. 

You must also disable automatic SONOS App update on the phone/pad(s).

Try rebooting your router and Sonos device, then update via the Sonos app—if it still fails, use the desktop app or contact Sonos support.

The latest Sonos app update has major issues and has disappointed many users.

None of which I’ve experienced, so they aren’t universal. Often, when there are issues, it points to a network issue, but not always, which is why more information in the original post is helpful. 

Sonos certainly isn’t perfect, but the most recent update hasn’t been a significant issue for most, based on the posts in this forum.