AWS Serverless Lambda (Angular Site in SSR) - Page content is getting downloaded as octet/steam content type header

We are using vendia aws serverless express package for running the angular app in ssr mode using express to be served from serverless. We upgraded from 3.x to 4.x

Handler Code lambda.js 3.x
`const awsServerlessExpress = require('aws-serverless-express');
const server = require('./server/main');
const awsServerlessExpressMiddleware = require('aws-serverless-express/middleware');

const AWSXRay = require('aws-xray-sdk');
AWSXRay.captureHTTPsGlobal(require('http'));

server.app.use(awsServerlessExpressMiddleware.eventContext());

const serverProxy = awsServerlessExpress.createServer(server.app, null);

exports.handler = (event, context) => {
// Please do not delete the below console. we waste too much time adding it again,
// as per ops there is no other way to get the request to lambda
console.log(JSON.stringify(event));
return awsServerlessExpress.proxy(serverProxy, event, context);
};

Handler Code lambda.js 4.x
`const serverlessExpress = require('@vendia/serverless-express');
const server = require('./server/main');

const AWSXRay = require('aws-xray-sdk');
AWSXRay.captureHTTPsGlobal(require('http'));

const app = server.app;

exports.handler = (event, context) => {
console.log('Event', JSON.stringify(event));
console.log('context', JSON.stringify(context));
console.log(JSON.stringify(event));
return serverlessExpress({ app })(event, context);
};
`

On checking the site rendering when lambda function is invoked when any page url is hit the content of the page is getting downloaded as content-type set as octet-steam. Could you please suggest and help