I’m encountering a similar issue. Have you managed to resolve it? I’ve noticed that my live theme is functioning correctly, but when I duplicate it, one of the CSS files throws the same error. Oddly enough, it’s identical to the source code of the live theme. I’m guessing it’s an issue with Shopify CDN?
Check the CSS file tiny.content.min.css exists in the specified location: /cdn/shop/t/14/assets/. You should be able to access the file directly by entering its URL in your browser. If the file is missing, you’ll need to upload it to the correct location.