I hope you are well today and thank you for your question.
Could you please temporarily clear and deactivate the WP Fastest Cache that you are using on your site so that I can troubleshoot it?
This can be due to plugin conflict on your site so please try temporarily deactivating all plugins except Unyson plugin and WpBakery page builder plugins and see whether everything works fine and then enable the plugins one by one to see which plugin is conflicting if any.