This indicates they are not relative links.
Check the HTML and ensure they are relative links, eg ./polyfills-es2015.1f07717b803649b0cda9.js or polyfills-es2015.1f07717b803649b0cda9.js.
If the link in the HTML is /polyfills-es2015.1f07717b803649b0cda9.js then that’s not a relative link and as the extension isn’t hosted in the root directory it’ll fail.