Socket.io connects and disconnects only for some clients resulting in package lost / unreliability

Describe the bug
A clear and concise description of what the bug is.
We have an nodejs websocket server with 3k+ concurrent connections. A few segment of clients disconnect and reconnect every few seconds/minutes.

We trigger the connection by joining to a room.

        roomsOnline.add(socket.handshake.query.roomId);
        socket.join(socket.handshake.query.roomId);

We use AWS ELB and their support says the load balancer has no problem.

On my machine i stay connected with the exact same roomId.

However his connection on the server end looks like this where it disconnects and reconnects. When we try to send the client a message using io.to(roomId).emit() it will only few of the messages instead of every message emitted

One of the clients that saw this behavior we tested with a different browser source from another websocket app and the messages work every time to his computer. The same client also had high speed spectrum internet.

To Reproduce

Our server settings - version 4.4.1

 allowEIO3: true, // false by default
    pingInterval: 9000,
    pingTimeout: 15000,

Server

const server = process.env.USE_HTTPS
    ? require("https").createServer(
          {
              cert: fs.readFileSync(process.env.TLS_CERT),
              key: fs.readFileSync(process.env.TLS_KEY),
          },
          app,
      )
    : require("http").createServer(app);

const { Server } = require("socket.io");

// https://stackoverflow.com/questions/48648555/understanding-socket-io-ping-interval-timeout-settings
const io = new Server(server, {
    // transports: ["polling", "websocket"],
    allowEIO3: true, // false by default
    pingInterval: 9000,
    pingTimeout: 15000,

    cors: {
        origin: "*",
        methods: [
            "GET",
            "POST",
            "OPTIONS",
            "HEAD",
            "PUT",
            "PATCH",
            "POST",
            "DELETE",
        ],
    },
});

Socket.IO client version: x.y.z

Client

    <script src="/socket.io/socket.io.js"></script>

    let socket = io({
          query: {
            roomId: last_part
          }
        });

Expected behavior
Expect all clients to stay connected

Platform:

• Device:
• CPU Name: AMD Ryzen 5 5600X 6-Core Processor
  CPU Speed: 3700MHz
• OS: Windows, Chrome/OBS

Additional context
I added a disconnect protocol which helped some clients that were international, but few clients still seeing this behavior

Server
let disconnectCheck = setInterval(() => {
            socket
                .timeout(16000)
                .emit(
                    "heart_beat_check_server",
                    "beating",
                    { running: new Date() },
                    (err, payload) => {
                        console.log(
                            "HEART_BEAT_PAYLOAD",
                            payload,
                            socket.handshake.query.roomId,
                        );
                        if (
                            err &&
                            payload &&
                            payload.version &&
                            payload.version >= 3
                        ) {
                            // the client did not acknowledge the event in the given delay
                            console.error(
                                "HEARTBEAT_ERROR_TIMEOUT",
                                socket.handshake.query.roomId,
                            );
                            socket.disconnect(true);
                        } else {
                        }
                    },
                );
        }, 17000);

Client
   socket.on("heart_beat_check_server",  (_, __, callback) => {
            console.error("heart_beat_check_server_client")
            callback({ roomdId: last_part, version: browserVersion })
        });

socket.on("disconnect", (reason) => {
          console.error("DISCONNECTED ", reason)
          if (reason === "io server disconnect" || reason === "io client disconnect" || reason === "ping timeout") {
            // the disconnection was initiated by the server, you need to reconnect manually
            socket.connect();
          }
          // else the socket will automatically try to reconnect
        });

Start with the server and client Socket.IO snippets, including the room join, heartbeat, reconnect handling, and ping settings. Compare the disconnect logs with the reported client and server behavior; done means identifying the cause of the intermittent disconnects and ensuring room broadcasts are not lost for affected clients.