So, this is most likely due to wifi interference . I’d encourage you to read the linked document.

There is a much smaller possibility of duplicate IP address clashes, causing your speakers to momentarily drop connection. You may want to try unplugging all Sonos  devices from power. While they are unplugged, reboot your router. Once the router comes back up, plug back in the Sonos  devices. 

Many thanks Bruce wi Fi dead spots are the Bain of my house. I do wish there was a waif covering the whole house 

Peter

If possible, connect one of your Sonos devices with an ethernet cable to the router. This will switch the system into SonosNet (wired setup) which may be more stable than running Sonos on your wifi.