I was able to resolve the issue, at least for now, by going to Advanced > System Tools > System Parameters and setting the Internet Port Negotiation Speed Setting to 1000Mbps Full Duplex.

I have the same issue. I have a 1 Gbps symmetric fiber connection. However, my download speed is 970 Mbps and my upload speed is 120 Mbps. This is connecting directly to the router using an Ethernet...