How to Fix Socket.IO 400 Bad Request Errors on AWS Elastic Beanstalk with Multiple Instances?

I'm running into some issues with Socket.IO connections on AWS Elastic Beanstalk. Everything works smoothly when deployed on a single instance, but once I scale up to multiple instances behind a load balancer, I keep getting 400 Bad Request errors.

Here's what's happening: in my client console, I see an error pattern like this:

`POST https://[redacted-domain].elasticbeanstalk.com/socket.io/?EIO=4&transport=polling&t=meh0duro&sid=WDHmjbJd7v5aE7mdAAeK 400 (Bad Request)`

And it mentions a connection error caused by an `xhr post error`.

I've enabled sticky sessions in the EC2 target groups as suggested in various forums, but that hasn't helped.

My setup includes a Node.js backend using Socket.IO and a React frontend, all hosted on AWS Elastic Beanstalk with an Application Load Balancer, currently running across two instances.

In my frontend code, I initiate the Socket.IO connection like this:

```javascript
socket = io(import.meta.env.VITE_SOCKET_SERVER, {
reconnection: true,
reconnectionDelay: 1000,
timeout: 10000
});
```

And my backend setup looks like this:

```javascript
const io = new Server(server, {
cors: {
origin: "*",
methods: ["GET", "POST"]
},
transports: ['websocket', 'polling']
});
```

Has anyone else faced a similar issue? What steps should I take to ensure that my Socket.IO connections operate correctly behind a load balancer with multiple instances? Thanks!