Maybe goto the Home Theatre master device ‘room’ settings in the Sonos App and increase the ‘Group Audio Delay’ buffer setting and see if that deals with the the network latency and resolves the dropout issue 

You may also want to refer to the wifi interference FAQ, as your speakers may be dropping connection to your router for one of those reasons. A home audio stream is much more “dense” than a standard music stream, and is consequently more subject to dropouts due to interference.