I've been reading online about slow upload speeds on various routers and haven't found a solution. 
 

ISP: Spectrum

Down/up are supposed to be at 400mb/400mb

Im only getting 300mbps down and 3mbps up.

QoS is disabled. 
Parental controls disabled

NAT Enabled

Negotiation speed setting: 1000mbps full duplex.

I've ran speed tests on wired and wireless from multiple devices. 2 computers wired and wireless. Mac and Windows. iPhone wireless. Xbox wired and wireless and am getting the same result. 
 

I've also reset it. Rebooted it. Updated the firmware and still no luck. 
 

I ran directly from my modem to my computers and am getting 350mbps/300mbps down and up respectively so it's not the Internet nor the devices. 
 

My ancient router performs better right now. How do I fix this? I'm thinking of just returning it and getting a different one bc this is impossible to work with at these speeds.