Lost surround and sub ( after update ?)

@Ken_Griffiths - firstly, thanks for all the help, patience and support. Very much appreciate your help and will take that advice forward and report back. My Sonos system is using a Boost which is wired into the back of my Netgear router. So I am not sure how much flexibility I will have for the settings you kindly provided me. 

Just so everyone is clear (and to make sure we are all on the same page) these are the symptoms that I experience. (Everything is freshly rebooted from the router / Apple TV to all Sonos Devices).

1. Using AppleTV, play multiple films on Netflix, and they seem to produce 5.1 (whether Atmos or 5.1).
2. Switch to Disney Channel and play a film, I notice that the rears and subs are not working from the start. However, the ARC is not outputting any bass frequency, so I assume that the ARC ‘thinks’ the sounds/frequencies are getting forwarded to other speakers.
3. At this point, I look at the MATRIX and although I am not an expert, it does seems to be all green. Which I am making an assumption that the network is not under stress. (See screenshot below). 
4. Leave the film playing, and after about 5 minutes I noticed the rear speakers experience a crackling effect - like they are spluttering into life. After another minute, the rears and subs come back on to provide full surround sound.
5. I have also noticed, on occasions but not always, that the rears seems to be out of sync with the fronts. Almost like there is a significant delay which causes the sound field to sound appalling. (However, this did not occur during this test, its just an observation I have noticed since 14.6 and has not been like this on previous versions).
6. Its not always consistent, but you can repeat the above and at some point that issue will occur. Some random combination of power on/off temporarily restores the sound. 

I have two subs in the systems and have tried this with only one - just to rule out the Primary /Secondary sub communication. The issue is persistent when using one sub or two.

When you think about it, the symptoms points to network communications - i.e. sometimes a delay, sometimes the speakers come back etc. But there does seem to be no evidence to support this, including when you look at the Matrix.

The real way to fault find this is if you could downgrade and run similar tests. However, there is no downgrade capability so you are a) unable to test/compare and b) stuck with a Sonos System which currently does not produce consistent surround sound. The latter is very frustrating as move nights in this house have stopped due to this issue! 

I appreciate I am probably going over old ground here, but I thought it would be good to summarise my observations so that people can compare with what they are seeing also. 

@Brad Porter,

Whilst waiting for any news from Sonos, or perhaps an update (if applicable), have you considered switching your system over to the local Netgear WiFi signal, even just as temporary measure, to see if it makes any difference? Here are the instructions (if needed) to try that, if you’re comfortable at trying the switch…

https://support.sonos.com/s/article/3209

I’m just curious, as the matrix in each case here, infers a non-Sonos device is acting as the STP root-bridge. Also my system, which is running on a WiFi signal is not experiencing the dropout issue, but that just might be coincidental.

Hi @Ken_Griffiths - out of interest, where do you see (on the matrix) that the non-Sonos device is being used for STP? I am looking but must be blind!!

I don’t see any Sonos device showing as the elected root-bridge (see this example..)

Edit: This shows a standalone wired Sonos Port as the STP root-bridge.

Thanks - yes, I cannot seem to get that to be the same in my system.

In way of an update, I moved all my speakers over the Netgear network and the problem still persists.  😞

@Brad Porter,
A ‘secondary’ node represents being cabled/wired and a ‘tertiary’ node shows a ‘wireless’ connection but in my own Sonos setup, in the distant past, whenever I was using SonosNet STP a Sonos device has been elected as the STP root bridge in my otherwise unmanaged network.

The root bridge has the lowest Bridge ID (often the Sonos Boost maybe elected, for example). All the decisions including which ports are the ‘root’ ports (the port with the best path cost to the root bridge) are made from the perspective of the root bridge.

Path cost – A switch may encounter one or more switches (junctions) in the path to the root bridge. All the paths are analyzed and the path with the lowest cost is elected. 

So I’m just assuming a non-sonos device on the local network is elected as the root bridge… unless it’s just a matrix labelling issue?

So whilst I can’t see why that would perhaps affect the surrounds/sub dropping out. I was just wondering if switching the system to a local WiFi connection with links back to the router, would make a difference and perhaps solve the issue.?

@Brad Porter 
Ah our posts crossed🤔. I now see you’ve mentioned you have tried switching all to your WiFi.. oh well, it was just a thought, as none of the matrix I saw posted in the thread here showed an elected ‘root-bridge’.

The root bridge will be elsewhere in the network, most probably the router.

In x.x.x.x:1400/support/review open the /usr/sbin/brctl showstp br0 link for any SonosNet node. The designated root is listed, as bridgePriority.MACaddress.

‘Secondary’ simply means the node is connected to the root bridge, without any other STP-aware nodes in between. It can be by wire or wireless.

‘Tertiary’ is everything else.

Thanks @ratty🙏. It just struck me odd that those that were seeing this ‘surround dropout’ issue, seemed to post a matrix that did not have a Sonos product elected as a root bridge, even those with a Boost, so whilst I understand by itself that isn’t an issue, I was just curious to see if switching away from SonosNet and using a wireless connection instead might make a difference to the surrounds dropping-out. It now seems it doesn’t have any impact, but thought it might be worth exploring, just to see.