I have had this problem since upgrading to Sierra a few months ago. I have a MacBook Pro (17-inch, Late 2011) with the Sonos Controller v7.0. When the MacBook goes to sleep the Sonos system will play for a while (probably whatever is in the buffer) and then just stops. When I wake up the MacBook, I see an empty Sonos Controller template that takes about 2 minutes to fill in with any data (my ROOMS, NOW PLAYING info, QUEUE contents and "Select a Music Source" menu).
I have seen a couple other threads with the sleep issue, but there doesn't seem to be a robust solution. I have tried reinstalling the controller and re-indexing the library but still get the same problem. As long as the MacBook is awake there is not a problem. Prior to the SIerra upgrade everything worked fine.
Has anyone else seen this problem and is there a solution? Is Sonos aware of it?