That suggests some sort of wifi interference in the 5Ghz range, which is what the Sub uses to bond with  whichever Sonos soundbar you use. However, it could also be a duplicate IP address issue, as the Sub gets its IP address from your router through its connection to the soundbar.

Thank you Bruce!

i am not an engineer how can I solve that?

The IP issue is easy, go to your router’s DHCP page and assign all your Sonos devices a static/reserved IP. Power down all Sonos, reboot router, power up your Sonos.

I’d do that before looking into the RF problems possibility.

Take a look around your Sub and whatever you have it hooked to for other 5 GHz devices. Try to give them 3 feet of distance from each other. Sometimes even a few inches more will help if getting the 3 feet is tough so try that.

You can wait for the disconnect / connect to happen again (if it still does) and submit a diagnostic to Sonos and then contact them with the number to have them look at the internal data.

Note, instructions for the IP address process will likely be in your router’s manual. It seems imposing at first blush, but really isn’t. Or at least hasn’t been on the two routers I’ve dealt with.