Policy-based routing issues

[CreativeUsername]

I've been trying to get this to work for several days now, but no luck.

My OPNsense setup has a default route that should be used for most traffic, and another uplink interface that is used for certain incoming connections from the internet, WAN2.

This traffic gets passed to another server that eventually replies (there is a port forward NAT set up for the IP address of WAN2).

I need replies to anything that came in through WAN2 to go back out through WAN2, but they get routed via the default route instead.

I set up firewall rules with WAN2 as the gateway to route the reply packages back through that interface, but I think stateful connection tracking is interefering with those. They work with UDP traffic, if I set the state type to none on the corresponding incoming rules.

How do I get this to work with TCP? Any firewall rules I set with a gateway for reply traffic just seem to get ignored.

Edit: I know this is a routing issue since it works as intended when I manually set a static route. This does not solve the problem, though. I need any replies to traffic that came in in through WAN2 to be routed back out that via WAN2, not just specific IPs.