@VinodhKumar 

Hello, we will do some troubleshooting first and try to fix it.

So the current Archer C20 will lose connection on 2.4GHz while 5GHz is stable? Try a mobile app to analyze the WiFi around you, review all the wireless channels. Next, review the wireless channels on the router. If the channels match that around you, an indication of overcrowded. Manually adjust the channels to lesser use channels.

There are possibly other wireless parameters that need tweaking, such as Power Transmit, narrow or wide band, etc. but start with the above and below link:
https://community.tp-link.com/en/home/forum/topic/200588​​​​​