Socket disconnect event doesn't always fire

Describe the bug
We have a React Native app using Socket.io to communicate with our servers.
Some users experience a quirk whereby leaving the app doesn't fire a disconnect event on the server for a very long time (hours).

See screenshot of some of our logs:

This also occurs upon making a io.in([...]).fetchSockets() call: those sockets still look open.

To Reproduce
N/A

Socket.IO server version: 4.8.1

Server

import { Server } from "socket.io";

const io = new SocketServer<
      ClientToServerEvents,
      ServerToClientEvents,
      { [event: string]: (...args: unknown[]) => void },
      SocketData
    >(server, {
      path: "/socket",
      serveClient: false,
      cookie: true,
      adapter: socketIoPubSubTopic
        ?
          createAdapter(socketIoPubSubTopic)
        : undefined,
    });

    if (socketIoPubSubTopic) {
      await io.of("/").adapter.init();
      log.log("Pub/sub subscription initialized for Socket.IO");
    }

    io.on("connection", async (socket) => {
    const userId = socket.data.userId;
    log.log({ userId }, `Socket connected for ${userId}`);

    if (userId) {
      await updateJoinedRooms(userId, socket);
    }

    socket.on("disconnect", () => {
      log.log({ userId }, `Socket disconnected for ${userId}`);
    });
  });

Socket.IO client version: 4.8.1

Client

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

const newSocket: TypedSocket = io(PUBLIC_SOCKET_HOST, {
        auth: !useCookies
          ? {
              token,
            }
          : undefined,
        path:"/socket",
        ackTimeout: 10000,
        retries: 12,
        timeout: 5000,
        reconnectionDelayMax: 5000,
        withCredentials: useCookies,
      });

Expected behavior
To always get the disconnect event firing.

Platform:

• Device: iPhone 14 Plus
• OS: iOS 18

Additional context
Add any other context about the problem here.

No repository files or tests are named, and the report has no reproduction steps. Start by reproducing the provided Socket.IO client/server setup on iOS 18, then trace the disconnect and connection-health behavior involved in the stale sockets. Done means identifying the cause and adding a regression test or clearly documenting the confirmed limitation.