If your theme uses Skrollr library, there is a chance that it will break the parallax effect of Visual Composer’ (VC) row element. The reason is that VC also uses Skrollr. Because this library only inits once, when VC Row tries to init Skrollr, it returns the previous object inited by your theme (VC’s JS is loaded after your theme’s JS file).
In addition, VC row uses JS to add “data-” properties to parallax row, so the previous Skrollr object cannot detect these properties. As a result, VC parallax row does not work.
To fix this, you will need to trigger the Row Behavior function of VC again so Skrollr can understand “data-” properties of parallax row again
The “vc_js” event is trigger after all VC functions have been called.
Let me know if this solution works for you.