How is the Beam connected to your TV?

It does seem odd, certainly. The next time it happens, before you ‘fix it’, submit a system diagnostic , and then, after you ‘fix it’, call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

An echo can occur in some circumstances where the Beam is grouped with other Sonos speakers in the same room - Are you using it grouped/bonded to any other Sonos products? If so, go onto describe the setup and maybe post a screenshot from the App showing the Sonos room(s) involved in the playback of the TV audio.

If using the Beam standalone and connected to the TV over HDMI, perhaps see what happens when you toggle on/off HDMI ARC/eARC in the TV settings… do things work better over ARC? Also set the Digital Sound Out to ‘Pass-through’ the TV ports. 

Last, but not least, If you have ‘other’ TV peripherals connected to the TV HDMI ports besides the Beam, see what happens if you either temporarily disconnect them from the TV, or switch off the CEC protocol on those other devices instead. (I recommend powering off/on the device too, after switching off CEC). 

Note: do not switch off CEC on the TV as that’s required for use with the Sonos soundbar when connected over HDMI.

Hope something in the above suggestions helps you to get to the root cause of the sync issue.

As well as the great advice above, what is the source of the TV signal when this issue occurs? I've had minor issues with SkyQ, around lip sync and mild echo, which is channel dependent and only occurs when streaming live 

If this happens again and the source is Sky Q, can you please pause the program and rewind approximately 5-10 secs and then continue play again. Introducing a 5-10 delay in the stream fixes the issue for me.

Via the cable that it came with. Not sure what type it is other than it's not HDMI

Hi, thanks for the suggestions. I'm using it as a standalone, it's not grouped to any other products.

It's a gen 1 so doesn't have an admin port so it's just connected to the tv with the cable it came with, looks like some kind of optical cable. I've seen you can get an hdmi converter, is it worth buying?

There's loads of other hdmi peripherals connected to the TV but as not currently connecting via hdmi surely these won't be affecting it?

It seems to occur no matter what the source is, be it Internet based such as netflix or from sky via the dish.

The Beam Gen1 is shipped with an HDMI 1.4+ cabled with HEAC support? The ends of the cable look like the attached HDMI image and it links to HDMI ARC (not eARC) on your TV, but there is also an optical converter in the box that looks like the second image attached (Optical to HDMI adapter).

Can you just perhaps look again and kindly clarify what connection you’re TV is using, if it’s HDMI, as I think, then you can go onto try the CEC suggestions mentioned earlier.

If you are using the Optical adapter, together with the HDMI cable, then the CEC issues mentioned can be ignored.

So sorry I'm an idiot! It's a Sonos Ray not a Beam and it has no HDMI port!

Ah no worries, if it’s going out of lip-sync over an optical connection, in that case, it’s more-likely (usually) something to do with the TV, or the cable. I would set the TVs Digital Sound Out to use ‘Pass-Through’ as a first initial step, assuming the TV supports that option. Also try another optical cable, just to eliminate that as part of the issue. 

Not to worry, but it does raise the question, due to the different nature of the connection, have you turned off the TV’s speakers? 

It's a Samsung TV, probably 10 years old. When I go to the sound menu, speaker settings, speaker select,  If I take it off 'TV speaker' and put it on 'External speaker' then I get no sound at all.

Then there’s something wrong with your setup. The TV’s speakers should be ‘off’, and the optical cable should be carrying the data to the Sonos. I’d recommend that you call Sonos Support directly to discuss it.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

You might find that the TV user manual ‘may’ suggest setting the now old TV volume to zero - this will not affect the optical output volume level, which is fuxed at full volume, but you might then need to use a different remote to setup/adjust the volume level of the Beam, or some users just choose to cover the TV’s infrared RX once the TV speaker volume is set to zero.  It all depends on the abilities of the TV itself.