Was reading many complaints. Eventually all complaints end with sending diagnostics to Sonos. But I didn't read about a solution, so wanted to add the solution I got. 

I have Sonos ARC connected to Samsung 75" smart TV. Arc connected to Hdmi 2/ Arc, also have apple TV and Xiaomi mi box S streamer.

To solve the problem where Sonos Arc disconnects. I had to go into the xiaomi streamer and disconnect its CEC settings.  

Problem solved.