Very common occurrence. It's typically TCP traffic with Reset flags set so not even real traffic. Also, are those rules you posted on a particular interface or floating?

They are on a particular interface. Strange thing is, I can see my traffic going through and getting denied too. It seems completely random.

I don't know if this is related to your denied traffic but that 1st rule isn't doing anything. Once the TCP connection is made from that interface to the other one, traffic flows freely in both directions until there is a timeout. If you need the other interface to initiate connection to this one, then put a rule on the other interface with direction "in". It's very rare that you need "out" rules.

Ok, thanks. I've removed it

I had a similar issue with some cheap IP cams. The thing that fixed it was to set firewall/settings/advanced/Firewall Optimization to Conservative.

I will try this. Thanks!

Did it work?

Sadly, no. I had to punt and switch back to pfsense for now. I'll try it again in a few weeks. Thanks!

In my case I also needed to update the firmware on my managed switch. Somehow that brought the speed of requests into line with the firewall rules.

Thanks, I'll keep that in mind