Netgate VLAN Gateway broadcasts on unidentified Port

Hey guys…I just found something today I can’t really explain.

By accident I saw that a Broadcast from my VLAN 30 Gateway/ Interface on UDP Port 40000 got blocked.
What makes me curious is not that it got blocked but where this Broadcast comes from??

Any Idea what this could be?

My Appliance is running on the latest Release and the only Package running on my Firewall is PFBlockerNG and 4 Open VPN Servers.