Just to make things clear, the address 172.27.9.255 is the broadcast address of your network, "a broadcast address is an IP address that allows information to be sent to all machines on a given subnet rather than a specific machine".
Therefore it makes sense that the APG sends messages to that address in your network, you can tested by doing a "ping" to the 172.27.9.255
Broadcasting is normal in any network; the APG40 are sending messages to the udp port 138 "This is the second port of the original "NetBIOS trio" used by the first Windows operating systems (up through Windows NT) in support of file sharing" The APG40s can not stop sending those messages because that will cause problems in their normal work, based in part on file sharing.
If you are experiencing a broadcast storm or a limited bandwidth, your solution is create a virtual network (vlan) for the APG40s, let's remember that a VLAN is a broadcast domain.
Hopefully this will solve your problem.