You are probably dealing with the same problem as these users:

Same issue 

Thanks @Herm212 and @GuitarSuperstar.

I read that thread and it’s possible the symptom I’m experiencing is related in some way, I’m not sure.

In my case I’m not losing audio on the subwoofer or surrounds -- the only manifestation I’ve observed is that the subwoofer audio is slightly delayed relative to the ARC.  I suspect that the audio synchronization software has a bug, but that’s just a guess as to what is going on.

As an example….last night I went to bed with the system playing correctly -- meaning good synchronization between the ARC and the sub.  This morning when I turned on my TV to watch some news I could tell that the subwoofer signal was lagging the ARC -- bass notes were slightly delayed relative to the rest of the audio.  I estimate this signal lag is a few hundred milliseconds.

I power cycled the ARC and normal sound was restored after it restarted.

(Side note:  This morning I also added a WiFi power outlet for easier power cycling of the ARC as a band-aid until Sonos is able to released updated firmware.)

I also have surrounds and sub delay echoing after the Arc.
I have read articles saying Sonos are denying there is a problem with this latest update but there obviously is.

Please Sonos rectify this as switching off the Sub and surrounds is not the home theatre setup I thought I was investing in with the Arc.

My setup is arc + one SL as surrounds

And I also have to experience the surrounds getting out of sync .

This has to stop.

Sonos….. we need an update with a correction of these issues

I have exactly the same problem. After resetting, rebooting my WI-FI and unplugging power repeatedly it still doesn’t fix the problem. The sub will just come on randomly and then go into this reverb mode. Come on Sonos, we didn’t pay three times the amount for a sound bar and sub to experience bargain equipment reliability. 

Same issue here since 14.6, but with rear Play:1’s to Sonos Arc. Sometimes they’re delayed, sometimes they just stop working entirely, I’ve had them distorting and garbled. I must have re-added the surrounds about 7/8 times now, power cycled the Arc triple that, solves it for a very short period then it comes back. Pretty disappointing there’s been no fix, and the mis-mash of statements and denials from Sonos means it’s starting to feel like amateur hour, which it really shouldn’t for a product like this.

Yeah i get reverb from sub and surrounds - it’s really obnoxious. I’m ready to throw this garbage in the trash and go Sony. 

I have same issue with subs and rear speakers being delayed. My setup is arc+2 subs+amp and 2 ceiling mounts for rears.

Just got my Arc and Sub 3 in the mail today and I’ve experienced this half a dozen times already. This was my first Sonos purchase and I’ve gone from excited to disappointed very quickly.

My system is on 14.6.1. Would a new software version not have cured this?

Same here.

Same issue. Just noticed it tonight and wow it’s annoying. 

I have never had lag echoing with my Sonos Sub 3 but I did get it when my 2 Sonos One SL's were playing surround sound, say, from a movie but since the last update (14.8.1) thankfully this problem has gone away!

When playing movies I just used to turn off the surround speakers as it was doing my head in which kind of defeats the purpose of buying surround speakers!

I just wish that the Sonos app had a way of rolling back the last software update like Windows used to do when I had a PC around a decade ago!

Same here for 4 weeks, with lots of support tickets and diagnostic numbers, regards, a sad owner

Same here. It seems to come and go. Today not only my sub but also the surround-OneSLs are affected.

Think I’m getting this sync issue as well, I have arc and sub gen 3, I noticed it during the last episode of Night Sky on Amazon prime during the end rolling credits.

If you do encounter the issue again, at any point, it might help the Support Staff if can submit a Sonos System Diagnostic Report asap and then contact/chat to them via this LINK 

HTH

Just spent 3 hours messing around with my setup before finding this thread ..

Its so bad.  I own more than 20 Sonos products in 2 different homes and this has ruined my experience with the fancy new Arc.

All my Gen 1 and 2 stuff still works great..  S1 for life.

FWIW rebooting the Arc fixes my issue temporarily as well.  

I have this problem. I reset the wifi and it sometimes helps it (for about 12-24hrs) and then I have to do it all again.

how is this not being addressed?

I’m not seeing how resetting the WiFi would help here, as the Sub uses a direct 5Ghz wireless connection between itself and the ‘bonded’ main player - although you might perhaps have wireless interference issues around your actual devices, perhaps? .. IMHO, I think trying to explore 5Ghz interference and maybe try to look closer at that issue, might possibly be a more effective longer-term solution.

Just thought I’d add my experience to this thread as I have the same issue on 14.8

I spent time chatting to Sonos support and in the end hardwired my Arc to my router (fortunately for me they are close to each other) and this has resolved the issue, so it definitely appears network related, but more likely Sonos rather than Wi-Fi as it was working before latest updates.

So for now, hardwire if you can until it gets fixed.

I have been expecting the same problem. Tried everything keeps coming back. This needs fixing Sonos!!!

so unhappy with my $2k system...arc, 2 oneSL surrounds and sub.  The surrounds and sub get out of sync with the arc creating a nausiating echo effect.  have the same setup at another house except for a beam and it sounds great.  Seriously Sonos, fix this issue, you're loosing major credibility.

Are you sure you have the surrounds configured as surrounds?  Correctly configured, the surrounds should not be playing the same signal as the fronts, so an echo would be impossible.  The only way for them to play the same signal is if you had them grouped, and a grouped speaker playing a TV source will indeed have an echo.