NAT acting erratically for UDP DNS

[D1m3b4g]

My settings:
NAT Outbound Mode: Automatic
NAT Reflection mode: Pure NAT
Enable NAT Reflection for 1:1 NAT: Enabled
Enable automatic outbound NAT for Reflection: Enabled

I am running a DNS server in the "WAN" space (172.16.0.10).
I have a private network behind a NAT on 192.168.101.x/24.

Anything TCP seems absolutely fine through from LAN to WAN on the NAT states.

Some UDP connections from the LAN side into the WAN seem absolutely fine also (see picture).
Some UDP connections that look absolutely identical from LAN into WAN just show NO_TRAFFIC (again see picture)

The picture shows some UDP connections working perfectly, and others being dropped. (I think?)
Is this PFSense acting erratically or could something else be wrong here?

I have no other firewalls running anywhere on the network and general connectivity and NAT translation seems fine, everything can ping, everything can route. PFSense just seems to be having issues with some DNS requests that use UDP and not others.

For instance, I can look up names via nslookup, but I can't get any boxes to register adaptor A records within DNS on the server.

Thanks
Paul