Why by refreshing page localhost on browser bundle_client is stuck on pending status?

I made super simple ssr app on node + react. By refreshing page on localhost on browser (Chrome or Safari, no matter) bundle_client.js is stuck on pending status.

GIT: https://github.com/antonkalik/ssr-app-chrome-issue

When I changed in src/server/index.js this:

  res.status(200).send(`<!doctype html>${markup}`);
  res.end();

to this:

  res.status(200).end(`<!doctype html>${markup}`);

pending disappears.

What's wrong with that? Where I messed up?

As you can see in package.json I using react 17 and webpack 5. I want to keep it up to date.

PROJECT STRUCTURE:

Screens from browsers