Probably because of the mess of routing you have there. Some devices on a /23 subnet, some on a /24. Not a big deal if you're purely routing, but throw a stateful firewall into the mix with some traffic only going in one direction through the firewall, and you have a mess.
Ideally, fix it so the masks of everything actually match. Everything on a /23 probably best if it's really just a flat network. Otherwise everything on /24 so the routing happens properly.
The "Bypass firewall rules for traffic on the same interface" option under System>Advanced, Firewall/NAT might suffice in the mean time. But likely only if you can ping across. If you can't ping, there's a more fundamental network issue at hand. The asymmetric routing will only impact TCP in most configs.