I am having the same problem. It seems like when navigating to certain in the admin panel, cysteme looks for the elfinder.en.js, can’t find it and creates a 404 error. See the screenshot: https://www.dropbox.com/s/8fi0qkzsg35o1sq/Screenshot%202016-08-01%2013.06.01.png?dl=0
This is the exact 404 url /wp-content/plugins/cysteme-finder/js/i18n/elfinder.en.js?ver=4.5.2
My site is dentalservices.net
The screenshot only shows only one place/plugin but I have gotten errors in other places in the admin panel as well. This particular plugin is the 404 to 301 plugin, I also noticed it happening when in the redirection plugin and also a custom admin panel and there are probably other locations as well. Let me know if you need more info. Thanks