Region : Hongkong

Model : Archer C7

Hardware Version : V1
Firmware Version : 3.13.32 Build 130329 Rel.36413n

ISP :

Dear all, would like to pick the brains of the experts here, as I am running out of ideas to fix this issue...
I have been using this Archer C7 for just about a year, didn't play too much attention to it until I switched to an ISP with provides optic fibre of 1000Mbps.

My speedtest on my laptop with killer e2200 gigabit Ethernet showed I am only utilizing about 25 % bandwidth.

The following are steps that I have done to try figure out the issue, but I am more or less ruled out most except the router...

1) Unplug everything, only Laptop --> direct connection to modem = speed test gives reading of ~870 Mbps download (ruled out ISP)
2) Unplug everything, only Laptop --> Archer C7 --> modem = speed test gives reading of ~250 Mbps download
3) Unplug everything & wireless off, Laptop --> Archer C7 --> modem = speed test gives reading of ~260 Mbps download (ruled out wireless)
4) Checked each of the cat e5 cables by switching each of them into direct connection to modem = all gives speed of ~850 Mbps down (ruled out cables)
5) Turned off WPS for both 2.4/5.0 GHz and IGMP proxy, retry step 2 = also speed test gives reading of ~250 Mbps download (ruled out WPS and IGMP proxy)
6) Reset to factory setting, retry step 2 = also speed test gives reading of ~250 Mbps download (ruled out configurations?)
7) Only connect my other desktop into router, and speed test also shows ~250 Mbps download (ruled out Ethernet card on my laptop)
8) Plug both desktop and laptop into router, both doing speedtest at the same time, one gets ~200 Mbps download , the other gets ~50 Mbps download (ruled out load balancing)

Any ideas, or I am having a faulty Archer C7?

Much appreciated.