By any chance are you running pfblocker, or know if pfblocker can cause any disruptions?
Update: after setting up avahi on ri4 my phone/tablet can see the soundbar across vlans but no other devices can cast.
11.160.30.1 is not a private internal IP address, that is a external real Internet Address. Try changing that ip range to 10.161.15.0/24 range.
Did you figure it out? I have the exact same problem and have tried everything and it’s driveing me nuts.