@Tony Sir , I have also tried downgrading and then upgrading the firmware but the problem is still intact .

My Wifi Router automatically disables wireless Radio and I have to connect the router using cable to again enable it from the settings. I have tried Hardware reset and it didn't solve anything ....

After upgrading the firmware to : 3.20.1 Build 200316 Rel.34392n (4555) The wifi speed went drastically down , I used to get ~44mbps speed over the wifi but now I get ~27mbps only (download)