I,
I have a similar problem (I created a separate topic for this, because I overlooked this one):
I have a Sonos 5 and a Sonos Connect:amp.
Although openhab.log was empty, I did notice these in events.log:
2017-11-12 10:14:54.235 [hingStatusInfoChangedEvent] - 'sonos:CONNECTAMP:RINCON_000E583F6C4A01400' changed from ONLINE to OFFLINE (COMMUNICATION_ERROR): The Sonos player RINCON_000E583F6C4A01400 is not available in local network.
2017-11-12 10:03:43.673 [hingStatusInfoChangedEvent] - 'sonos:PLAY5:RINCON_000E58834E6A01400' changed from OFFLINE (COMMUNICATION_ERROR): The Sonos player RINCON_000E58834E6A01400 is not available in local network. to ONLINE