AC1200 Limits Ethernet Speeds

So I bought this router a while ago to get better coverage around my flat (walls are shading signal like crazy for whatever reason). And I was lazy for a while to fix the issue of the slow ports and I thought it was my cable being slow and limit my speeds. So I went and bought certfied cat5e cables that are capable of my speeds (overkill honestly as I only get 250mbps). And now I can verify that this router even though it techncially is certfied for 300-900mbps I only get 100mbps regardless of what cables I am using. Both WiFi or Ethernet.

I have tried checking the settings in the router by logging in, couldn't find the QoS settings as it just doesnt exist and that was the issue that turning it off, fixed it for most people. I reset the router too and went through the whole setup process again but still the same slow connection for whatever reason.

I have updated the firmware to V1.0.0.82 but, yeah, no changes. If anyone has an idea how I could go about fixing this, that would be handy.