LG SJ9 Soundbar Goes Offline When XG is Connected

Hello,

I'm having a very strange issue I'd like assistance troubleshooting. I'm using a Sophos XG 135 as my home firewall and all has been going OK until I purchased an LG SJ9 soundbar. The LG SJ9 soundbar does not appear to allow any inbound communication when the Sophos XG 135 is connected to the network. Removing the cable that connects my LAN switch to the Sophos XG immediately allows me to communicate with the soundbar. I can see that the device appears in my arp tables, and I am able to ping it from the Sophos itself or any device routing through the Sophos such as an SSL VPN client. I am not, however, able to communicate with the device even from another device plugged into the same dumb switch. I've added exceptions everywhere I can think of for my Soundbar but have come up empty. LG support is obviously not able to assist as they just ask me to "unplug the unit from the wall and plug it back in." I've also opened a support case with Sophos, but I figured I'd throw this out here in case anyone else has experienced something like this.

What I've tried:

Create a business rule that allows access to all services and destinations from the source IP of my soundbar.

Create exceptions for the soundbar in Advanced Scanning.

Create a "Web" exception for the soundbar.

Stop all Sophos security services.

Disable "Pharming protection" and all other options on the Malware scanning page.

I'm stumped to say the least.