1Gbps Full Duplex has 100x slower upload than 100Mbps Full Duplex

Notice how on 1Gbps Full Duplex, I only get 0.18 Mbps upload:

Yet on the lower 100Mbps Full Duplex, my upload speed is normal:

"Auto Negotiation" leads to the same issues as 1Gbps Full Duplex.

I've tried three different ethernet cables from the router to my computer and have had the same issue on all three. The one I'm using now has been tested to not have similar issues with other computers. Additionally, there aren't upload speed issues over the Wi-Fi from the router. Large Send Offload v2 is off for both IPv4 and IPv6 (speeds get even slower when they're on).

Is this intended behavior? Or some sort of resolvable issue?

Had the same problem initial (super slow upload), same network card. Took me a while to get to the same point (1Gbps slow upload). In my case it was a PC connected to the wifi router via LAN. When I connected my macbook via wire and USB-C network interface to the same router, everything worked fine.

As it turned out, the reason was in router's Fragmentation Threshold (complicated setup with router connected via wifi to another router). I set it to 2300 (while default is 2346) and the problem went away.