Hi @Andor.

Welcome, thank you for reaching back to Sonos Community.

If your seeing a question mark in your home theater setup it means that the left surround and right surround speakers are missing.

Possible causes are wifi interference or speaker issue.

Make sure the speakers are always turn on and the most common issue is Wifi interference 

Let us know if it works. If you need help with any other information, please be sure to let us know.

Thank you for the answer, well when I start watching something on tv everything goes back to normal, the sub and the ones reconnect nicely without doing anything. The Arc never disconnects.

Hi @Andor.

Welcome, thank you for reaching back to Sonos Community.

Just update us for any issue you might encounter, other users and peers can also help you right away.

If you need help with any other information, please be sure to let us know.

Some folks see issues with dynamically assigned addresses, using your router’s DHCP page to assign static/reserved IP addresses see an end to the disappearing devices issue after doing that.

It really doesn’t bother me, it only happens when they are not used, when I’m using them (watching TV, playing, listening to music through them) it never happens, they stay connected, all 4 of them. What I observed is that one of the devices always stays connected when the other 3 shut down/disconnect. I was just curious if this is a normal stand by behavior or not, if it’s some kind of “low power” mode the Sonos devices fall back to when not in use for longer period. 
 

This is not normal behaviour, but as it seems to cure itself in time to not bother you, you could choose to let it rest.

Well, I’ve managed to resolve the issue by connecting the rear left Sonos One SL speaker wired to the router, now the speakers appear properly connected even if not in use. 

Sonos does not recommend connecting only surrounds by cable though. But if it works…..