Library not found

Using a gallery I receive the following message:

DevTools failed to load source map: Could not load content for https://huppenbroich.de/wp-content/plugins/gallery-by-supsystic/src/GridGallery/Galleries/assets/js/lib/hammer.min.js.map: HTTP error: status code 404, net::ERR_HTTP_RESPONSE_CODE_FAILURE

What might be the reason? This happens also in other pages with many pictures. Short galleries seem to be okay.

The page I need help with: [log in to see the link]