I have a Beam 2 and a recent LG tv.  I was encountering the problem with eARC / LG Simplink where the TV would only stay on Bluetooth for 2 seconds before switching back to eARC.  The solution was to use the optical adapter.  The TV receives the optical end of the adapter, and the Beam receives the HDMI end.  Using this arrangement, as far as the TV is concerned, there is _no_ eARC connection.  Therefore the problem goes away and you can reliably stay on Bluetooth.

Just ran into this same problem.

Sonos ARC. Samsung Tu8000 and wh1000xm4. Quite shocked 1 Year on it hasn't been resolved.

So any practical software only workarounds that doesn't involve turning off the SONOS? 

Thank you. 

Turning Off Simplink was the only thing that worked for me. Previous Soundbars I used with there same LG TV, including Q990b don't force the TV connection back to eArc.

But you won’t have the Dolby Atmos feature.

What are my choices if I want to return the Arch and buy a sound bar that doesn’t have this issue?

I don't have any issues with Samsung or LG Soundbars. Additionally, Samsung Soundbars have a remote and an option to turn off the Soundbar.

Or would be great if the Sonos app add a feature to turn off the Soundbar so that prove have the option when Simplink option doesn't work.

I have the same problem. Lg g1 Sonos arc. It would be very nice if it can be fixed 

Same problem with my LG G2. Turning off simplink doesn’t work and it turns back on almost instantly.

Unplugging the HDMI from my Beam Gen 2 is the only solution so far.

Then I would perhaps contact LG customer support - as Simplink (CEC) should not be doing that - I have their C9 OLED with the Sonos Arc attached and two other (different models) of LG TV with Ray & Beam attached and in all three setups ‘Simplink’ stays disabled when I turn it off and want to use Bluetooth or headphones. It maybe a firmware issue on your model of TV.

Same problem here. LG G2 plus ARC. Can't switch to headphones:// I have few speakers from Sonos. But I think I'll change arc to sth else :/// in G2 I can't turn of CEC :/

What happens when you disable Simplink/Auto-Power Sync and then switch the TV sound out settings? 

Simplink turns on immediately itself

:(

I would call LG Support, as I have 3 different models of LG TV in my home, including their C9 OLED and all of them allow me to disable ‘Simplink’, that’s with either a Sonos Arc, or Beam (gen2) attached, to use either a Bluetooth connection, or headphone port. My thoughts are it’s a TV firmware bug that requires an update, but see what their Support Staff say.

I’ll call them. I'll come back with answer here. We'll see

I have the exact same issue here. I stopped at Best Buy (it’s where I bought the system), my local TV dealer that sold my LG C2, I called Sonos and LG 2 times. No solution was found, except physically unplug the Sonos Arc from the TV. SIMPLINK cannot be disabled (comes back on after 2 seconds), and nothing in the Sonos app is able to stop the TV to automatically switch audio output to HDMI (ARC). LG representatives says it’s Sonos fault. Sonos representatives say it’s LG fault. My TV dealer never saw such issue on any other system, thus I doubt it’s a Standard issue that would come from CEC/eARC/SIMPLINK specifications. Or other manufacturers more wisely bypassed the specs for consumer convenience. The only solution I can find is to return my 3000$ system to Best Buy, cause I don’t want to physically unplug the Sonos arc each time I want to use my headset, which is the only solution that a Sonos representative gave to me yesterday.

Try inserting a CEC blocker in the HDMI connector. You’ll also need to configure ARC to use IR Volume commands.

Thanks buzz. I bought a Bluerigger between the Arc and the LG C2, and now I have no more sound transiting at all, even if I set the volume reasonably high with the Sonos App. When you were mentioning a « CEC blocker », did you have a specific model in mind?

I have no favorite, the one that you have should work. You’ll likely need to enable Simple Link on the TV and enable IR Volume control for ARC. Configure the LG remote to control a fictional A/V system. The model number is arbitrary, just don’t pick a model that is nearby, then train ARC to use those commands.

LG G3 and Sonos Beam 2 owner. Same issue here 

Had an LG B8 with the same issue, kept unplugging the hdmi from the ARC to use Bluetooth headphones, eventually the ARC plug broke off the circuit board on the TV, then had used a optical hdmi adapter to use Sonos beam, and able to connect headphones.

Today upgraded to an LG C2  thinking this issue may have now been resolved. Guess what, same issue. Not even bothered to use the ARC, SO FRUSTRATING.

All this technology and a simple thing like this can't be fixed, 

 Doesn't look like my future buys will be LG or Sonos if they can't come together to fix this problem.

Just thinking an issue would be resolved is pour preparation. Especially since Sonos does not acknowledge there even is an issue……

To be fair I did buy the b8 five years ago, so naive  have I been to think things would have moved on by now, but what do I know? I'm just old, and didn't check everything the TV could and couldn't do.

lumbered with it now.

So I have the same issue with my Sonos arc and my LG C1, the solution I found is to go to 

Sound>Advanced settings> Turn off eArc support. 

Then goto General>HDMI Settings> Turn off SIMPLINK

You should then be able to use any Bluetooth headset without the output automatically switching to the soundbar.

You'll need to reverse those settings once done and enable eArc support manually. 

The other option is to unplug your soundbar or use a smart switch to turn it off so you can use a Bluetooth device

Same problem here . LG G1 and ARC.

Followed steps suggested by nathanfernandes and it works fine, Simplink stays off and my BT headphones connect ok.

Just have to reverse steps afterwards. It’s just two changes in settings so no biggie for me , as I only use headphones occasionally late at night when other half goes to bed.

Hope this helps others.

The current implementation of CEC, which Sonos uses, allows a single audio ‘sink’. The TV manufacturers would need to change their firmware and internal electronics, as that’s where the CEC controller (computer) exists. Sonos is just following the specification where they report themselves to that computer as an audio sink.

Some TV manufacturers keep the optical output disconnected from the CEC system, which is often why you see the suggestion here to connect the Bluetooth transmitter to the optical output. Unfortunately, it’s not all, from what I’ve seen.