Nodejs app suddenly started to act differently

This part of code handles the login authorization routing in my app

const express = require("express");
const authController = require('../controllers/authController');
const indexController = require('../controllers/indexController');
const router = express.Router();

router.use("/login", (req, res, next) => {
  if(req.session.loggedIn) {
    res.redirect('/account');
  }
  next();
});

router.use("/account", (req, res, next) => {
  if(!req.session.loggedIn) {
    res.redirect('/login');
  }
  next();
});

router.get('/', (req, res) => {
  res.redirect('/login');
});
router.get('/login', (req, res) => {
  res.render('login');
});
router.get('/log-out', authController.logOut);
router.get("/account", indexController.getAccountData);

module.exports = router;

There were no problems and it was working fine till recent days.

I haven’t change anything in this file nor authController nor indexController.
When I make a change (in other parts), nodemon restarts the app and I automatically jump to login page cause obviously all sessions are destroyed. But I get an error in getAccountData function (Error says req.session is undefined).

As you can see there’s no way for the app to reach that function with no sessions set.

I have to restart the app again to act correct.