1) Problem is not related to the number of categories it’s related to one of the third-party plugins that you use – Jetpack by WordPress.com. Once we disable plugin everything is ok. It seems this plugin conflicts with some WPBakery builder scripts. Contact plugin developer to fix this.
2) It’s related to general site speed and time of script loading time. Script closes the categories and while it’s loading you see them opened. Install cache plugin, optimize images to reduce the page size – speed up your site to avoid this effect http://prntscr.com/pdym9e
