If you updated to WordPress 4.9 (published on November 15, 2017) it's possible you are experiencing a few wired problems on your installation. These are known issues you can experience:
- Visual Composer not working with Firefox browser (please use Chrome);
- Visual Composer Backend Builder jumping to bottom on actions;
- ColorPicker (Hex Color) selector missing in Palette options;
- Self Hosted video background not working;
- Self Hosted video toolbar not full-width.
On November 17, 2017 we released the Uncode 126.96.36.199 and on November 28, 2017 we released the Uncode 188.8.131.52 with the new version of Visual Composer that fixes Page Builder issues with Firefox browser. We are sorry for these issues that arise from incompatibility between Visual Composer and the new WordPress update.