pfSense UPnP service always stops working after a few minutes since last service restart

Fergo

If I enable UPnP in pfSense 2.7.0, it seems to work fine. I can run the command upnpc -r 1234 TCP and I get the response:

List of UPNP devices found on the network :
 desc: http://10.0.0.1:2189/rootDesc.xml
 st: urn:schemas-upnp-org:device:InternetGatewayDevice:1

Found valid IGD : http://10.0.0.1:2189/ctl/IPConn
Local LAN ip address : 10.0.0.93
ExternalIPAddress = [redacted]
InternalIP:Port = 10.0.0.93:1234
external [redacted]:1234 TCP is redirected to internal 10.0.0.93:1234 (duration=0)

I can run this command over and over again, with no issues. But after ~5 minutes or so, running the same command will give me:

No IGD UPnP Device found on the network !

I can restart the service and it will again work for several minutes before invariably not responding any more. I don't see anything in my firewall log except for "Default deny rule IPv6." Certainly nothing related to SSDP. My firewall rules are all default, consisting of just:

WAN: Block private networks
WAN: Block bogon networks
LAN: Anti-Lockout Rule
LAN: Default allow LAN to any rule
LAN: Default allow LAN IPv6 to any rule

ps aux lists: /usr/local/sbin/miniupnpd -f /var/etc/miniupnpd.conf

If I restart the UPnP service and run tcpdump on pfSense, I get the following when running upnpc from my desktop:

00:41:29.931828 IP 10.0.0.93.62316 > 239.255.255.250.ssdp: UDP, length 137
00:41:29.985376 IP router.home.arpa.ssdp > 10.0.0.93.62316: UDP, length 433

After waiting ~5 minutes I run the same command from my desktop and nothing shows up in tcpdump except for the occasional:

00:48:59.585197 IP router.home.arpa.42061 > 239.255.255.250.ssdp: UDP, length 473

The contents of /var/etc/miniupnpd.conf:

ext_ifname=vtnet0
port=2189
listening_ip=vtnet1
secure_mode=yes
presentation_url=https://10.0.0.1/
uuid=a03cd731-69f5-1480-71f4-91f53368e99
serial=A03CD731
model_number=2.7.0-RELEASE
allow 1024-65535 10.0.0.40 1024-65535
allow 1024-65535 10.0.0.93 1024-65535
deny 0-65535 0.0.0.0/0 0-65535
enable_upnp=yes
enable_natpmp=no

If I run miniupnpd on pfSense in debug mode I can also see it reacting to my upnpc commands, but after ~5 minutes the process is still running (with no error messages) but has absolutely no reaction any longer when I run upnpc on my desktop.