If the ‘other’ A/V devices seem to be working fine, but the Nintendo switch isn’t, I’m surprised you contacted Sonos Support - I would have personally started by contacting Nintendo. Then moved onto the ‘man-in-the-middle’, which is LG Support for the C1 TV, particularly as the Sonos HT product is the last thing connected in this instance and playing okay with the other products. The Beam can only play the audio as soon as it receives it. Which makes me think it’s something more likely ‘upstream’, rather than the Sonos device in this instance.

I think the problem is PCM 5.1 with LG C1 and not the device. For example, when I set stereo on the Nintendo switch, there is no issue anymore. As I said, I had some troubles with PS5 too. I tried a longer session on it and the issue still occurs (but less often than the switch).

I found others post with the same issue : 

Multichannel PCM 5.1 dropping out since 14.10 update | Sonos Community

(4) LPCM 5.1 audio cutting out Apple TV and Switch Beam gen2 : sonos (reddit.com)

Unfortunately, I can’t change my TV, so I guess I need to wait for a hypothethic firmware update on my C1 or just return my Sonos system.

I’m using the older LG C9 TV on firmware v5.30.25 with an Arc/Surrounds/Subx2 and I have an even older 2015/16 LG TV with a Beam/Surrounds/Sub (using a Feintech eARC extractor) and each seem fine with Apple TV/Multichannel Linear PCM 5.1 (uncompressed) audio, so it’s probably not a Sonos issue.

As mentioned, the HT products can only play the audio when it gets to them and I’m not personally seeing any audio lip-sync, or interruption issue here and I’ve had both those HT setups for some time. I have had 3 or 4 updates on the LG C9 TV since purchase late 2019/early 2020. Not noticed a lip-sync issue with any codec along the way. It plays DTS 5.1 and Dolby TrueHD fine too from Blu-Ray discs.

In your opening post you mentioned that your TV ‘digital sound out’ is set to ‘pass-through’. If you’re absolutely sure it’s not your Nintendo Switch,  then just to mention, whilst trying to research this issue for you, I came across some reported issues with the C1 TV and some users reporting a similar lip-sync problem who mentioned having some success with their ‘digital sound out’ set to the default ‘Auto’ setting - so perhaps give that a try. If no luck, I would go onto speak with LG Support too, as they maybe able to mention if they are perhaps working on such issues.

Thanks for your answer. I have no problem with lip-sync or with other formats like DTS/DD/Atmos, just some random audio cuts out with PCM 5.1.

I tried to set “digital sound out” to “Auto”, no more cuts out but the signal is no longer PCM 5.1 but PCM stereo. 

I sent an email to LG to find out if they are aware of the issue and if they were planning to fix it with a firmware update. 

A little update:

I find out that either the Switch or the PS5 had audio cutting out every minute when I plug them into HDMI3 or HDMI4 port on my LG C1.

On HDMI1 port, audio keeps cutting out but much more rarely (like 1 or 2 times per hour).

Something weird is definitely happening with my TV. 

Maybe switch off ‘CEC control’ on both the PS5 and Nintendo Switch and see if that makes any difference and just leave the CEC operation continue between the TV and Beam only.. I’m just wondering if those other connected devices are perhaps attempting to steal the CEC focus away from the eArc connection. It’s worth a try, at least. 

I switch off cec control on both the PS5 and Switch but it did not help. When I tried to disable “simplink” on my C1, the toggle turn off during 2s and turn back on. Maybe because earc is enable.

Yes you definitely need Simplink ‘ON’ on the TV, the suggestion made was to just leave CEC control ‘off’ on the connected devices, but if that didn’t work then it’s not something that’s causing the issue.

I assume you powered ‘off’ your devices after you disabled CEC and ensured the TV remote was not working with the PS5 and Nintendo switch? - the other option, is to uncable those devices one at a time and power cycle the TV to see if it’s a particular connected device, although I guess the issue coukd lie with the TV itself.. maybe wait and see what LG say.

I tried by powering off my devices but it did not help. 

LG contacted me and they told me that EARC issue with Sonos and C1 was fixed with last firmware. They asked me to do some tests and I will contact us again next week if it does not fix the dropouts. 

By the way, I don’t know why, but a best « answer » has been marked for this topic but there is no solution right now, and it’s not an isolated issue with the Nintendo Switch but with every devices connected to HDMI to my TV with a PCM 5.1 signal. It doesn’t seem to be an isolated problem:

I’m using MC LCPM with an Apple TV and Sonos Arc/Surrounds/Sub, but have the LG C9 OLED and that’s working fine with no dropouts, or issues, but maybe the recent LG firmware hasn’t fixed the issue on that particular C1 model - I did mention earlier that some online posters said they had to switch their Digital Sound Out to ‘Auto’ to get their TV’s to work correctly, but appreciate you’ve tried that.

The only other thing is to perhaps monitor the issue and take a few System diagnostics (note their references) and speak with the Sonos Support Staff again and perhaps between that and the ongoing LG Support, the matter will get resolved with an update. I suspect it’s an LG issue ‘still’ with their firmware, but I guess only time will tell if that is the case.

Yeah this isn’t true. This thread shouldn’t be shown as answered. It isn’t a Switch issue, it’s a PCM 5.1 issue that Sonos refuses to fix or comment on.

Have the same issue with the LG G2.

It didn’t occur on my C9 previously.

It seems to be a problem with the G1-2, C1-2 because they use a different chipset from the C9.

I’ve commented on the other thread linked here. Spoken with Sonos support today and sent them diagnostic, they’ve promised to look into it.

No firmware update to my TV has fixed the issue so far, and it occurs with every 5.1 PCM audio source so it’s got nothing to do with your switch or ps5.

Did you have the chance to test the firmware update LG mentioned? Which version is it? Did it help?

Same issue here with the following setup:

Nintendo Switch / Apple TV → LG C1 → SONOS Beam Gen 2

At one point I could see the cutouts exactly every 60 seconds while playing BotW. So I contacted SONOS support and they analyzed the support files. It appears that from the perspective of the Beam the input signal just drops.

So at this point I am focusing on the TV as the culprit. Somehow I am wondering if the uncompressed LPCM signal is filling up some kind of buffer on the TV which gets dropped at regular intervals because the processor is unable to pass through the audio signal fast enough.

And I also observed a difference between the different HDMI ports. Some are behaving worse than others.

Have the same issue. Lg G2 with a Sonos beam (gen 2) and 2 One SL. Have the ps5 set to 5.1 and get audio dropouts every min. 
 

also happens on Nintendo switch when in surround mode. 
 

seems to be an issue with the beam as arc users don’t seem to be reporting this issue

Toggle between SonosNet and Wifi - ie if you using Wifi, try SonosNet or vice versa. There is a help article on Sonos Support on how to do this. Can’t seem to be able to paste links here.

Do you mean The wireless and wired systems FAQ? 

Hi @Eruvatar et al

We now recommend you reach out to the TV manufacturer (LG) as this behaviour is also occurring with different soundbar manufacturers (so it’s not a Sonos-specific issue).

Alternatively, please utilize different audio formats from McLPCM 5.1 (e.g., McLPCM 7.1, DD+, etc).

I hope this helps.