That would most often be some sort of wifi interference  in the 5Ghz range, as the surround speakers use that to connect to your Arc. 

One other thing, beyond the solutions in that linked FAQ, is to try a network refresh. The surrounds get a proxied set of IP addresses from your router through their connection to your Arc. It’s possible that your router is giving them duplicate IPs by mistake. Unplug all Sonos devices from power, then reboot your router, and give it a couple of minutes to reload properly before plugging back in you Sonos devices. 

This solution doesnt work, the sound from one sls disapear for 3sec and apear it lasts in 40s intervals during listening or watching netflix

Problem solved, router settings for channel 11 on 2.4ghz wifi