@techie28 

If you use such a semi professional network, please tell us more detailed information about its setup. Especially to what kind of device the Sonos Connects are wired to via lan cable. If you use an ethernet switch, it has to support STP protocol and igmp snooping. 

Thanks this is helpful, I believe IGMP snooping is enabled on the vlan but will check.  core switch with the sonos connect is a 3750. 

It appears to be working well again. After another reboot. That said, this is helpful and gives me some insight as to how dataflows are managed since I really haven’t had the time to setup a span port and analyzer.   Much appreciated. 

I recommend that you refrain from Factory Reset without further consult. As you have discovered, the Factory Reset has not cured any fundamental issues and it has wasted a lot of time. Finally, it destroys diagnostic data available to SONOS support. I suggest that you submit a diagnostic while the system is operating and again within 10 minutes of a failure. Keep track of the confirmation numbers and follow up with phone support. Occasionally, a staff member will reply if you post the numbers here.

Since a reboot seems to help for a while you might try setting static/reserved IP addresses for your Sonos devices and see if after a network/Sonos reboot if things get more stable.

I spent many days and hours of troubleshooting avoiding this solution while seeking a cause to my problems but in the end I tried it and it worked.

@Schlumpf Thank you. Super helpful. CGMP/IGMP Snooping was in fact NOT ENABLED. Swallowing my pride here. Should have gone back to basics to verify the config …. which hasn’t changed in years, but obviously I didn’t save the running config somewhere along the way.  USER ERROR… i hate that :-) 

@techie28 

Thx for feedback… And good to hear you got it working again.

Don‘t hate yourself… Sometimes making mistakes is part of being human.