I have installed “Fast Velocity Minify” Plugin and deactivated it, because it ruined the mega menu dropdowns, probably it is causing issue, i am not sure.
It doesn’t work because of the Comet Cache installed on your website. It adds this unnecessary comments to AJAX requests and breaks the JSON data structure https://gyazo.com/5f6ce5bcc6f1ae9557bff0f89d3c8f45