Suspecting that there's a firewall which truncates the bound socket.
Are you using external imports which require internet access in your HTML/JS files? such as:
Some of the imports open and establish new connections which remain in stale open state, and some firewalls, if exist, may terminate the main socket which initiated the connection.
If you have external dependencies, try to download the offline package instead, and include it in your project (to avoid downloading it every time the page loads).
So that the above import tag becomes: