Thanks for writing in! You can check out more information about this issue from this knowledge base article:
In most cases, this is cause by a caching plugin like Autoptimize or W3 Total Cache. If you have a plugin that minify the JS and CSS files, that might contribute to the issue. Please keep in mind that JS and CSS files were already minified. Minifying it again will be an overkill and would result to an issue.
Hope this helps.