Bandwidth issues/packet loss on ZBox CI325 Nano

[Tainavaa]

I've got a setup with drops installed in the walls of my home that lead to a patch panel, where each drop plugs into a Juniper EX4200 switch. The switch is connected to the LAN port of the OPNSense gateway.

Using iperf from one drop to another in my home using my desktop as one node and a laptop as another node, crossing only the switch, I read transfer rates of ~1 Gb/s. I installed the iperf plug-in for opnsense and tested from multiple drops (the same drops I tested that gave full speeds) to only get anywhere between 400-450 Mb/s transfer rates when testing iperf normally. Testing iperf where the server sends data, however, nets me just a bit more than that - maybe ~460-480 Mb/s consistently. When plugged directly into the demarc (optical terminal), I my full rated 300 Mb/s up/down as advertised by my ISP. When plugged even directly into LAN from the gateway to the demarc, I get between 115-125 Mb/s down, but 300 Mb/s up.
I've tested the cable from the switch to the gateway 3 times, as well as used the cable in an iperf test between drops (getting full speeds).
I thought perhaps maybe it was the NIC, so I swapped LAN and WAN NICs, to find out I get the same speeds on both NICs.
I've ensured all hardware offloading is disabled and whatever settings are on that page.
The CPU never reaches a high load while testing iperf, it's always a relatively low load so it isn't being maxed out.
Testing directly from PC to LAN interface does not help, so the switch is not causing the problem.

tl;dr My ZBox running opnsense is getting less than half the bandwidth it should with notable packet loss (not mentioned earlier but packetlosstest.com shows this), and I have no idea what it could be. Has anyone experienced an issue like this? Any guidance is appreciated.


NOTE: I've plugged my old router (Linksys WRT AC1200) into the demarc and plug my desktop into that when I need full, reliable speeds and keep opnsense plugged into that so my network stays the same, and I can plug my desktop into the switch for when I need access to my LAN resources. A really lazy and inconvenient fix but it works for now.