The empty files are likely waiting for a response from the app, and eventually will time out.
Try adding a line like this to serve the files that don’t need processing or special routes …
app.use(express.static('public'));
Depending how your app folders are structured, this might be /app/page instead of public, or you may have multiple folders to serve.
app.use(function(req, res) {
if(res.status(500)) return res.sendFile("/app/errors/500.html");
if(res.status(404)) return res.sendFile("/app/errors/404.html");
})
Note that this sends no response for any other status, you may want to add a default response.