Having trouble with ports on my game server docker container

[PlanetVaster]

I am running a game server using Docker (didstopia/rust-server) on the latest TrueNAS Scale nightly (7/20). I'm having an issue I've been debugging for a few days now and can't figure out: The server uses ports 28015 (UDP), 28016 (TCP), and optionally 28082 (TCP). All the ports work on my LAN, but port 28015 (the main game port) isn't working on the public internet, even though the other 2 work on the WAN. The container has a static IP set, the ports are forwarded on my router and the firewall on the router is configured to let them through. I'm spent the last few days debugging, unable to find a solution. Seems the problem is because it's UDP since the other 2 ports which are TCP work fine, the issue seems to be either with my TrueNAS configuration or with my Docker setup.

I'm very confident the problem isn't my router, because when I was running the server in a VM it worked fine, so it seems to me Docker is causing the issue but I'm not sure how/why.

 

[PlanetVaster]

Update: I switched to use "host network" and now It works. So the bug has something to do with UDP port using a static IP on external interface.