ASUS RT-AC68U speed will throttle down to 100/100mbps

Hello,

Since November 2018 have I been having issues with my ethernet speed.

I pay for 250/250 which I got when I setup the LAN for the first time but after having that speed for maybe about a month it throttled down to 100/100.

I tried swapping the router/cables, changing firmware both Asus stock firmware, Asuswrt-merlin and DD-WRT (which is my current firmware), changing duplex on the router but nothing worked.

After a couple weeks I figured out that if I repeat the following things my...

ASUS RT-AC68U speed will throttle down to 100/100mbps