White Overlay with Advanced File Manager Plugin

I recently had to switch from WP Filebase Pro to Advanced File Manager by modalweb to manage documents on a website I support. When I tried to edit some Custom CSS code I found I could not see the code. I have a lot of active plugins but after disabling them all and re-enabling one at a time I discovered that Advanced File Manager was the cause of the problem. It doesn’t affect the CSS or JS but it requires that I deactivate the Advanced FileManager plugin in order to make any changes to the CSS files.