Issue between WP 4.0.1 and Visual Composer

Hello guys, I have a project which uses the WP CMS, I was running it for a long time on 3.9 WordPress version and everything was fine, I saw that there is 4.0.1 security update for <u>all previous versions, therefore I installed it. I don’t like installing wordpress updates often, because I use 15 Plugins that run my website and it is 99% likely that the website crashesh until the plugin update. The same happened with updating from 3.9 to 4.0.1. The problem – I use visual composer but it doesn’t work (under Firefox). There is a JS conflict in theme.min.js that says “m.css is not a function”, I don’t know why, because even after deleting the theme.min.js from the tinymce/ folder, this continues happening. So my question: how can I return to 3.9 version ( I have database backup only ), or how can I fix this issue? ( The issue is between WP 4.0.1 and VC Plugin ). Thanks!