Is the Playbar hardwired direct to the router itself? If not, then I would certainly try that (if practicable) to rule out anything else along the path and even try a different network port on the router and Ethernet cable, to also rule out those things. Of course it might be the WAN connection too or a combination of things, although that seems less-likely if all works fine with your other (newer) Sonos players.

Yes it is hardwired.  My fear is that it will take a newer Sonos sound bar to overcome (pricey). 

That won’t be the case, unless there is an electrical failure in your specific device. Since the inception of Sonos, they have never forced upgrades of any speaker, they all remain supported. The only devices that have been ‘retired’ are not speakers, but an old 30 pin iPad connector, and a physical remote control.

At the least, I’d suggest a reset of your local network, by unplugging the PLAYBAR from power, then rebooting your router. Give the router a couple of minutes to boot up before plugging the PLAYBAR back in to power. 

Are you “reserving” IP addresses for SONOS?

My Playbar is operating perfectly wirelessly. And if you have wired your Playbar then "older wifi" could not possibly be the problem.

Does the problem arise when just your Playbar is playing or does it only arise when grouped with other speakers? 

…and you might end up with the same issue if the problem lies elsewhere‍♂️. I would certainly try the things suggested and if you cannot resolve the playback-interruption, then within 10 minutes of encountering the issue, submit a system diagnostic and note, or post, it’s reference back here and then contact/chat with the Sonos Support Staff via this LINK and see if they can see any issues with the device.

I have the exact same issue. My Playbar used to be connected to a 8-9 years old Samsung LCD TV via optic cable, and I had no problems playing music or watching TV. A year ago I bought a new Sony LED TV and watching TV is not a problem, but when I am listening to music, wether the TV is on or off, the music cuts out 1-2 times per minute for about 5-10 seconds.

I have tried EVERYTHING, but the only thing that works, is when I disconnect the optic cable from the TV. I thought I was the only one with this problem, nice to know it is not me. Think it is a software/signal issue, between Playbar and TV. Yes the Playbar is old hardware, but bought it from new about four years ago, so should at least last for another half decade without disconnecting the wires when switching between music and TV.

Wow, I’m having the same issue. It started when we replace our old tv to a new Sony OLED/

I called Sonos support, and I was instantly told they are aware of the issue (music interruption), and it is the Sony television. Wow, I would never think about that, I was sure it’s a network issue.

As a workaround, they suggested to set RS232 control to serial in the tv’s menu. I need to see yet if it helps/

Wouldn’t you just switch it off?

https://www.sony.com/electronics/support/articles/00154270

https://www.sony.co.in/electronics/support/articles/00154270

It was off…

It is a Playbar, so I would assume the other option also should not bother it (rs232 through hdmi) as it doesn’t have an hdmi port on it, not like the Arc or other Sonos devices.

Let’s see it tomorrow 

Hello. I have the same problem since I changed my TV to a sony Oled XR-77A83K.
When the optical cable is connected I have music playback cuts, even TV on standby. When I unplug the optical cable, I no longer have a cut. This comes from Sony TV optics.
I hope a solution will be found!

Did you try the above suggestion mentioned by @nabateus?

I searched on my Sony Oled XR-77A83K TV, and I can't find any adjustment concerning the rs232, as described on the link
https://www.sony.com/electronics/support/articles/00154270
Maybe I'm doing it wrong, but even on the sony manual for my tv, I can't find anything about the rs232. If anyone has a solution ?

If you haven’t done so already, I would maybe speak with Sony Support and see what they say, as the connected Sonos HT device (or any optical connected device for that matter) will only play what is sent to it in a timely matter - it’s a one-way connection only to the speaker. So the issue will likely be down to the Sony TV (or the connecting optical cable) I suspect. I would just see what Sony Support Staff can recommend.

Okay. Yes for me the problem comes from the tv. Before I already had a Sony Bravia tv, with optical output and I didn't have this problem. I will contact sony support and let you know.
Thanks very much.

Hey guys,

Here is the update: I can confirm, seems like the problem is solved. Cannot tell witch action fixed the issue, the RS232 settings change, or applying the latest firmware on the Sony (however I was behind only one version, maybe about two months ago),

but finally I can enjoy music on the Playbar without interruptions. 

Hello everyone,
I explained my problem to Sony and here is their answer:

Dear Mr Roman,

I am following up on your email concerning the sound cuts on the sound bar when it is connected to the XR-77A83K television.
I am sorry for the concern you are having.
Please rest assured that the TV has the latest software version: PKG.6.6070..EUA
if not, update it:
https://www.sony.fr/electronics/support/oled-tvs-android-a80k_a83k_a84k-series/xr-77a83k/software/00283238

In addition, I will report your request to the dedicated service.
Also note that Sony does not guarantee full compatibility with third-party devices.
Please accept, the expression of our distinguished feelings.
Michael

SONY SUPPORT TEAM
SUPPORT: http://www.sony.fr/support/fr

Obviously I am not satisfied with this answer and answered them that it is not normal that their TV, in standby, continues to send a signal via the optical cable, which disturbs the reading of another source on my soundbar. Compatible or not compatible, it should not happen! I hope they will correct this issue.
Then, Sonos, can also try to correct this problem, by not taking into account the optical signal, when the source is not the TV!
In fact, I endure and wait, hope.

I thought that the RS232  fix was finally the solution to by Sony-TV connected, wired Playbar’s problems when playing from my (wired) NAS containing my music library - and for about 20 mins I had interruption-free music but then - a cut out as before. I had one more about 20 min later. I think that this is less frequently than in the past but alas, the problem isn't fixed. My TV’s software is upto date and my(unwired) Playbase which is also connected to a Sony TV doesn’t have the same problem. 

Has anyone had any update on this. I’m pretty sure I’m getting the same issue. Dropouts in audio (not the TV audio) but any other source on my playbar e.g. Spotify or Turnable via Line In on a play 5.

Only the playbar drops. Tried turning off RS232 no luck.

So my update it's definitely the Sony TV as if I unplug the optical audio it all works fine with no dropouts.

So for a bit my workaround was to do that 

Now I've discovered that if the TV is on (with optical audio in) but I set the Sonos to play line in or stream or whatever no drop outs 

Weird TV off but optical audio plugged in and I get dropouts TV on no drop out 

My current crap workaround is Turn TV on and either set picture off or run a screensaver 

Same problem here . . . . Playbar optical from TV.

All works fine but streaming music etc drops with optical connected.

It used to do it with my LG TV and now with my newer TCL as well.

A simple fix I’ve found is by putting a fairly cheap optical switch with remote inline.

When I stream, I change the optical switch to a different input - problem solved. (kinda the same as disconnecting optical)

It's annoying why is a turned off TV putting out something on the optical out? And more to the point why does the Sonos listen to it, when it's set to a different input? Annoying, now I've discovered just leaving the TV on (as a massive digital photo frame) while I listen to music works. I can live with it. Can't see Sonos fixing it.

I do the same, leaving the TV on, and broadcasting a radio source or music library, I don't have the problem. Sonos could indeed not take into account the TV signal (which disturbs) when using another source. I'm surprised Sonos can't find a solution!

Can’t you just disable Autoplay on the Playbar? Then if a signal shows up on the optical input it will be ignored, until you explicitly switch to TV on the Sonos app.

I deactivated Autoplay TV on Playbar, but unfortunately it does not change anything, when listening to music library or radio, the sound bar regularly cuts about 7s. Thanks for the idea.