I upgraded the BIOS on my PCEngines APU4B4 from v4.11.0.4 to v4.11.0.5 and experienced a 60-70% reduction in network traffic through the device. I also noticed an increased number of interface errors that I hadn't noticed before.

I'm running OpenBSD 6.6 (amd64) with all errata to date applied.
Interfaces are Intel i211AT.
Switch is a UniFi Switch 8 port switch running the latest stable version, 4.0.80.10875.

I ran multiple rounds of iperf3 tests on between two separate devices in separate VLANs.
4.11.0.5 average forwarding was around 160 Mbits/sec
4.11.0.4 average forwarding was around 500 Mbits/sec