I've been having some issues lately with Dante on my SG300's as well. we've added more edge devices and sometime the extreme ends of the network are not coming up, or show in DC but produce no audio when patched. odd as you can ping all of the units but they still don't work properly.
we narrowed the issue down to our SG300's, and have found success by removing the multicast and IGMP settings as recommended by the Yahama guide. all other settings from the guide remain. haven't gone further than making it work, hopefully have time in the next month or so to see just why this is causing us grief. thinking maybe IGMP should only be on in one switch, we have as many as 12 switches in play end to end. going without IGMP at all for now, no issues so far.
for the record, our network for Dante is its own VLAN with no other traffic. this VLAN (and others) trunk between switches. we use Cisco SG300, TP-Link managed and unmanaged switches across the network.