I’ve identified the problem. It’s the Media Grid element in V.C.
Each time the media element is used it creates an admin-ajax.php request. Even if the media element is not set to display for that screen size.
I’ve already replaced several ‘media grid’ elements, and it has made a huge difference to the page load speed (4 times faster than before). But I still have three ‘Media Grid’ elements in use which causes 3 admin-ajax.php issues.
I’ve emailed you an FTP account so you can still take a look.