Server Middleware returning next(new Error(.......)) is not sent to the client

Describe the bug

I have a middleware that returns an Error object in some particular situation. I see the error in the server's console but I do not see the error being sent to the client.

Server:"socket.io": "^4.5.0"
Client: "socket.io-client": "^4.5.0"

To Reproduce

Socket.IO server version: x4.5.0

Server

import { Event, Socket } from "socket.io";
import { ServiceLayer } from "../services/serviceLayer";
export const userActivateMiddleware =
  (serviceLayer: ServiceLayer, socket: Socket) =>
  async (event: Event, next: (err?: Error) => void) => {
    const user = socket.data.user;

    if (user === undefined) {
      return next(new Error("User Email Not validated"));
    } 
    return next();
  };

// Elsewhere:
socket.use(userActivateMiddleware(serviceLayer, socket));

Socket.IO client version: 4.5.0

Client

import { io } from "socket.io-client";

// Listeners
socket.on("connect_error", socketConnectError);
socket.on("error", socketError);

function socketError(err: any): void {
    console.log("Socket Error", err);
}
function socketConnectError(error: Error): void {
    console.log("socketConnectError", error);
}

// How the request starts
socket.emit(MsgUserPixelKind, message, (response: MsgUserPixelValidation) => {
    manageResponseFromMsgUserPixel(response);
});

Expected behavior
The emit is performed and the NodeJS Socket.io servers receive the request. I can set a breakpoint and see the request getting inside the middleware. In the case I am testing, a rejection, I see the code getting into the if and executing the return next(new Error("....."));. I am expected to get the client to be notified somehow (by the connect_error or error or by the callback. However, nothing.

Platform:

• Device: Macbook Pro
• OS: MacOS 12.1

Additional context
Looking at the Chrome's network ws tab, I see the request sent which collaborate that I can have the NodeJS server hit my breakpoint. However, no response. The callback is not called either.

No repository files or tests are named. Start with the server socket.use(userActivateMiddleware(...)) middleware and compare its next(new Error(...)) path with the client's connect_error, error, and emit callback listeners. Reproduce the Socket.IO 4.5.0 case and establish which client-visible error path should complete the request.