Hey @shameemreza
I had a feeling that the issue was with WooCommerce Shipping plugin. I first deactivated WooCommerce Shipping and tested the checkout page; The problem was gone.
Next, I reactivated the plugin and tested the checkout page once more. The problem came back.
Then I uncheck the address validation box in WooCommerce shipping setting and tested again. The problem was no longer there.
I believe the problem lies within the newly added validation at at checkout update in WooCommerce shipping.