Slow internet speeds only on one PC

[Synful]

Alright everyone,

 

Long time lurker, but I had to join for this one. 
I am having a bizarre problem with my main rig. 

I pay for 300/15, dual band router, 24 lane modem. Currently, on ANY device, except for my main driver I get near (>260). This includes all Wifi devices unless they are 2.4Ghz and my Wifes rig with an identical MB. On my main driver, I am only getting about 60/15.

 

I am at a loss... Other computers on the same port using the same cable are getting the speeds they should, so it must be something on the rig itself. 

 

Things I've tried:

Uninstall/Reinstall drivers

Different Ports

Different PC on same port

Checking BIOS settings

Disabling all power saving junk

Forcing the adapter to a gigabit negotiation

 

Full power cycles inbetween all of the above steps as well.

 

Short of reinstalling Windows, does anyone have an idea?

 

My Specs

Intel 6700K OC'd to 4.7GHz

ASUS Maximus Hero VIII

G-Skill Trident 3200 x16Gb

ASUS Strix 1080

Windows 10 Pro 1809 (yes i know, it deletes stuff)