Arc SL: LG C2 Keeps switching back to Arc SL when trying to switch to other Sound Outputs like TV speakers

Have you tried disabling eARC first and then disabling Simplink?

This is a function of CEC (Simplink), and not particular to Sonos. I’d second @GuitarSuperstar ‘s suggestion. 

I have the same issue. Is there any reason eARC actually needs CEC to work?

I have the same issue in my C2 and Sonos Arc setup.  I have tried to contact Sonos and LG but both couldn’t fix the issue. 

I have the same problem. Cannot not switch to any other audio out like Bluetooth headset without tv switching back to ARC about 2 sec later. Any update?

Turning the ARC autoplay off down not prevent this. 

Typo, I meant to say turning the Arc’s Autoplay off did not correct this. 
 

My work around has been to unplug the Arc’s HDMI plug then any other audio out selection will stick. 

I have been bugged with this for a very long time. My solution: go to settings > all settings > connection > device connection > disable auto device detection and simple link. This will enable you to choose another sound output source. This will work till you switch back to ARC source again. I use Sonos arc and had the problem of switching automatically to sonos arc. Now I can use my BT headphones when I want. Sadly this method has to be restarted every time you switch back to hdmi arc. Try and let know. If anyone else finds a different and stable fix please let me know. 

Glad to know I’m not the only person with this issue.  I keep praying for an LG or Sonos update to fix this.  Essentially I end up “fighting” with the TV.  The only way I can get things to work is just try over and over again-- either to a.) turn SIMPLINK off - it wants to turn back on or b.) change audio input to something besides HDMI ARC.  This happens literally every night when I want to use my bluetooth headphones on my optical connection...some nights I win the battle in a minute, sometimes I give up after a few minutes and end up just pulling out the eARC connection.
 

@GuitarSuperstar @Airgetlam How does one disable eARC?  (Even if I could do this it would only be temporary as I normally want it on, so I’d have to switch it back every time.)

@Weird Panda I’m not seeing the option for “Connection” on the LG settings.

If your TV is equipped with eARC, look for the eARC Support setting and switch it to OFF.