Load Balancer - 400 Bad Request

Summary:

I am getting 400 - Bad Request when invoking public API Gateway backend point via Load Balancer.

When this endpoint is invoked without going thru the load balancer, it works fine.

Content (required):

Public Load Balancer has got backend set which is associated to the public API Gateway.

Public API Gateway has got deployment which just fire a http request "https://api.weather.gov". When invoked directly using APIG Deployment endpoint, it returns status "ok"

However, when it is invoked using Load Balancer endpoint, the traffic is routed to correct deployment but with an error message "400 Bad Request". I have also changed the header size at the load balancer listener to 64KB.