No audio when AirPlay to Volumio instance on different subnet/vlan

My network is partitioned into multiple vlans where I connect my wifi device (that I stream from) to one vlan and my Volumio devices sit on another. I can switch the vlan I’m connected to by connecting to its associated ssid. When I’m on the same vlan as Volumio I can stream without issue. When I’m on another vlan however, streaming “looks” like it’s working but I get no audio.

My gateway (UDM Pro) supports mDNS and I see all of my devices regardless of which vlan I’m on. Whether streaming from the same, or a different vlan, the Web UI shows the correct song meta data (name, etc) and playback progress.

When things didn’t work initially I suspected my network firewall configuration. Since the Web UI updates with the correct song data and progress, I suspected that control packets were successfully reaching Volumio but song data may be getting dropped at the LAN firewall. After capturing packets on the Volumio device for both scenarios I see no difference in the packets received – I have control commands on TCP 5000 and what I believe is song data to UDP 6003. The command packets look identical – song meta data and setting parameters.

Additionally, journalctl -f provides the same log output for both scenarios.

I’m running Volumio 3.251

I would appreciate any tips on a direction to continue to investigate or if someone has already tackled this issue and has a solution. Thanks.