@Kevin_Z 

I reverted back to the version 1.2.0 Build 20191014 and so far its working fine.

I paid for a 160Mbps connection and am getting the rated speed for now, need to monitor it for a few days.

I bought the router a year back maybe dont remember the exact time. the issue started happening around 2 days back when I updated to 1.2.1

I first updated to the latest version 1.2.1 from 1.0.1 and faced the said issue of throttling.

I initially updated as my wifi range was kinda shoddy at some places and would drop to 49Mbps Link on 5Ghz. But now after facing the throttling issue on the said 1.2.1 firmware I downgraded to 1.2.0 , as any lower than that is not possible as TP-Link locked firmware downgrade below 1.2.0.

Can't really ping now as all is working great, but let me give an example: On youtube when I see stats for nerds the speed shown there is always above 50000Kbps all the time, but with the latest 1.2.1 firmware it dialed back to below 5000 even after hard reset to factory settings and video started to buffer even at 480p. Whereas at the same time when I tested direct from ISP modem to pc lan it worked as expected 50000Kbps+ speed.

Now I am monitoring the router with my PC to see if the throttling issue comes back again.