I will try 1400 MTU again. Don't think it is a coincidence, as Netflix was not working for more than few minutes for last two weeks, since I got Bharat Fiber connection. It used to work nicely with ADSL connection. It still works with ADSL. ( I still have my ADSL connection ), Meanwhile, I changed the MTU at Modem (mine Optilink ONT). Go to WAN Settings and there you will see MTU.
I thought MTU modification is not necessary thanks to "path MTU discovery" steps taken when a connection is made to a server. but maybe some misconfiguration in Netflix servers or bsnl network causing this low MTU to allow it to speed up things. good to know.