In core-thin folder I have "core.material.css" for example that have this reference:
/*# sourceMappingURL=core.material.thin.css.map */
The name of the map file is core.material.css.map thou which in turn results in "Error: An error occurred while trying to read the map file at core.material.thin.css.map".
If I check the map file it have reference to "core.material.thin.css" that also doesn't exist.