I have two Beam units connected to Two LG OS TVs  they have worked faultlessly for two years connected to the HDMI(ARC) inputs alongside the HDMI input from a SKY+ box then along came Sonos 2. 

I have spent the last 3 weeks using every combination of set up routine reading all the forums and some common sense and have ended up using the Optical adapter which is acceptable up to a point and that point is... why should I have too ?,

What have the Sonos engineers changed that has caused this?  The System will work with the Beam in the ARC  socket completely without fault with the TV recieving terrestial TV signals from the antenna socket and no other HDMI connection used.

Next stage ..as soon as you switch to HDMI 1 the sound either mutes or defaults to internal speakers

Emtering the TV setup and selecting HDMI(ARC) out has no effect as the beam looses the conection, open the APP and try to re connect the unit has no effect as it contunually reports no  connection  or  another HDMI signal is interfering unplug all other HDMI signals, which I do and setup completes ……. sometimes but not always, sometimes it just gets into a loop, sometimes it resets the beam and  looses it  from the system completely.

It annoys me that I have to use the sonos app to setup the beam to the TV I only want system that works as it should and I would not recommend sonos to anybody based on this fiasco.

Any ideas out there for a work around please