What router are you using? Try unplugging all the speakers from power for a couple of minutes and rebooting your router.

Are you able to wire just the Arc to the router with an ethernet cable?

Right now I’m using a ARRIS cable modem, but I've also tried a Linksys mesh and just an old Linksys, same problem with all three, so it’s not a router issue.  Tried rebooting  components with different routers and same problem.  My original plan was all wireless and it worked for a month, now it only works if a components are wired.  Wiring just the ARC didn’t fix the problem.

You could still be experiencing wireless interference:
https://support.sonos.com/s/article/3286?language=en_US
 

If you remove the Sub and surrounds from the Arc in the Sonos app and re-add them, does it make any difference?

Do you have any other Sonos speakers wired to your router?
 

Run a diagnostic within 10 minutes of the Sub and surrounds disconnecting and report the confirmation number here so Sonos staff can take a look at it.
https://support.sonos.com/s/article/141?language=en_US

Note that the SUB and surrounds connect to the Sonos Arc using a 5Ghz channel created by the Arc itself. If turning on the TV is creating enough interference to that 5Ghz signal, the devices will disconnect. Note that it’s possible that it’s a process of turning it on, rather than a constant level of interference. 

Those devices do not connect to your router directly, but get proxied from the router through the Arc. 

It might be worth checking to see if there’s a firmware update to your TV to address that potential issue. In general, the four inches between the bottom of the TV and the Arc should be enough, there’s certainly an aspect of the FCC checks designed for external RF interference rejection in every electronic device. It’s not infinite, though... 

And frankly, I’d really be tempted, then next time it happens, to submit a diagnostic, and contact Sonos directly to see what the logs say. 

I’ve tried moving the ARC a couple feet from the TV to see if it’s RF interference, still has problems.  I have already tried disconnecting the HDMI from the ARC and turning the TV on.  It disconnects when the HDMI is plugged in not when the TV is turned on.  It also disconnects when I plug it into the optical adapter connected to the TV or a BD Player.  So it’s the starting of an audio stream that appears to cause the problem not powering up a TV.

I’ve tried reseting everything and reinstalling the system, no effect.

I plan to run a diagnostic tonight and send the results to Sonos, but their chat bot was no help.  They do have a phone number but I really need to get this fixed by text, email, chat or this site.

I understand that the Sub and Surrounds use a proxy through the ARC on a dedicated 5GHx network.  Before retiring I design embedded firmware and RF communications systems.  I tried running all components through my wifi instead of the Sonos network, had the same problem.  I have noticed that when the ARC disconnects from the Sub and Surrounds they also drop off the network both when it’s using a Sonos 5GHz network with the ARC as a proxy and when all components are connected through my wifi.  

I’m wondering if it could have something to due with regional restrictions.  I’m in Puerto Rico.

Can you perhaps post two screenshots of your Sonos App’s ‘Settings/System’ list showing your devices when they are all working together nicely ..and another to show what happens to them when the surrounds drop and stop working… thanks. Can you also kindly confirm that you have not switched off the wifi/wireless adapters on any of your HT devices.

I realized the problem went away when the TV was unplugged and I had the Sonos ARC connected to the BD Player. So I turned off the TV’s wifi and wired it to the router.  Problem appears to be fixed, everything is working.  I tried moving the ARC a couple feet from the TV and still had problems, so this TV really has a bad interference problem that popped up on the last firmware update.  So all you LG CX owners beware you might need to turn off the TV’s wifi and wire into the router.  

Crap the problem is back, SONOS has a really poor ability to handle RF interference that makes wireless operation impossible in a condo.  I’m in a condo and I think I’m getting interference from the other wifi networks in the building.  So I’m going to use all the SONOS components in wired mode and use TP wifi routers in client mode to carry the audio streams.  

I’m surprised 

That's not making much sense to me as I understood it was the ‘surrounds’ and ‘Sub’ that were ‘dropping’ from your Arc. Those connections use the 5Ghz band and that’s not normally a crowded band, even in a condo environment, not least that radio band would normally not travel far through neighbouring walls, unlike the 2.4Ghz band - I suspect there is perhaps something else amiss here if it is your HT surrounds that are disappearing and losing their ‘bonding’ over what is an ad-hoc connection to the main HT player and not a connection to the local WiFi router.

Forgive me for asking this ‘perhaps silly’ question @mchorn64, but are you certain that the two surrounds and Sub are ‘bonded’ to your Arc and not ‘Grouped’ with it? Only a ‘grouped’ setup here, would actually explain why the other speakers always dropout, when you power on the TV.

The surrounds and sub are bonded to the Arc and they work fine if I power cycle all the Sonos components after the TV is turned on.  But they disconnect when the TV is turned on.  I did determine that the Sonos ARC does not disconnect from the Sub and Surrounds if the eARC is unplugged when the TV is turned on, but when I plug it in it disconnects (this indicates a firmware bug and not RF interference).  I did send a diag. to Sonos when the system was broke 1649291719 and when it is working 5777962.  I hope someone at Sonos is reading this because the chat bot is of no help and I’ve received no email responses.  I’ve been working on this for two weeks now.  I’m using the iPhone app to monitor the Sonos components.

I know other visitors to the forum here have both the LG CX and Sonos Arc, but not seen them mention a case where the bonded surrounds dropout when the TV is powered on - it’s like something is ‘strangely’ affecting the 5Ghz ad-hoc connection between the surrounds and main HT player, particularly as the Arc stays connected and working with the TV?

It maybe best/easier to simply give the Sonos Support Staff a call instead. I suspect they may want to run some tests with your setup anyway to see if there are any hardware/software issues.

I was talking with them, hope they can figure it out.  I noticed in the ARC support/status page that the ARC phy is getting 10’s of thousands of errors.  So maybe it’s a H/W problem.  Here’s the status report:

contents of /proc/ath_rincon/statusDebug info for INFRA mode at 17191263Mode: INFRA (sonosnet)Operating on channel 2412Home channel is 2412HT Channel is 5805RF Chains: RX:4 TX:4RF Chainmask: RX:0x0F TX:0x0FMax Spatial Streams: RX:4 TX:4Noise Floor:    0 dBm (chain 0 ctl)Noise Floor:    0 dBm (chain 1 ctl)Noise Floor:    0 dBm (chain 2 ctl)Noise Floor:    0 dBm (chain 3 ctl)PHY errors since last reading/reset: 5214378     Region: 1Node 5C:AA:FD:CC:EB:7B - FROM 00  00 : TO 00 : STP 00 : MODEL 28.1: KEY -1  00  00Node 54:2A:1B:18:79:25 - FROM 00  00 : TO 00 : STP 00 : MODEL 32.1: KEY -1  00  00Node 5C:AA:FD:CC:EA:C7 - FROM 00  00 : TO 00 : STP 00 : MODEL 28.1: KEY -1  00  00

Looks like the format got trashed when it got sent, here’s the importent line “

PHY errors since last reading/reset: 5214378  “

Don’t know if those are internal or external but there sure is a lot of errors for a device that was just powered up.

The sonos support had me change the network channel to 1. I already tried 6 and 11. The TV needs to be off for a least an hour before turning it on to have the problem.  So now I just need to wait and try it out.

That PHY Error report is not always very useful because the error report is reset after a reboot or page refresh. If you want to keep a log, say for different times of day or time since the TV was reset, pick a constant time interval between page refreshes. The data will not likely be 100% consistent because for high counts, a fraction of a second difference between your responses could result in a difference of hundreds of errors.

Certainly, if the report drops from hundreds of thousands to hundreds, there is a hint somewhere.

How are the PING times to the devices? Are you seeing dropped packets?

I reset everything, set it up on the floor with a BD player for audio source and an old Linksys router for the wired connection to the ARC.  It’s more than 12’ from any interference and all sonos componets are within a foot. Set everything back up and as soon I started an audio stream the ARC disconnected from the Sub and Surrounds and now it will not reconnect.  This problem has nothing to due with the TV or interference.  It’s either a firmware bug or hardware bug in the Sonos componets.  I’m going to hammer on sonos to get this fixed. 

Sonos has been no help so far, I got dropped from the phone twice and dropped from the chat twice.

I had Sonos support working on it for about a hour Friday night, the problem didn’t get fixed and it was getting late so I went to bed.  Saturday the system was working and I could not break it, it broke every time I started and audio stream for the last month and now it works!  I don’t know what got changed but if it keep working I’ll setup my theater again and keep my fingers crossed.  I still have an open ticket with Sonos support so if it stats to fail again I don’t have to start from scratch with there support people.

Submit a diagnostic now (while the system is working)and keep track of its confirmation number.

I submitted a diag., it’s been 36hr sense it started working.  I put the components back where they were when the problem first started.  They still work fine.

Now it’s broke again, same problem it loses the Sub and Surrounds when the audio stream starts.

I had 9 days of it working.

Just double checked, if I power cycle the ARC it reconnects to the Sub and Surrounds.  But as soon as I start an audio stream from the TV or Internet it disconnects from the Sub and Surrounds.  I put all the Sonos speakers on the floor close to each other, and away from all other signal sources, I have the same problem so it’s not interference.

Most of the time it will recconect to the Sub and Surround after the audio stream is stoped.  I’m using the iphone app to monitor the Sonos system.