When running on a machine with multiple network interfaces only the primary interface works. Im my use case sACN is on an isolated network. This can be fixed by specifying the IP of the desired interface when calling _socket.addMembership.

As a work around I am calling

dmx.on("listening", function() {
    const multicastGroup = "239.255." + (universe >> 8) + "." + (universe & 0xff);
    dmx._socket.addMembership(multicastGroup, dmxInterfaceIP);