What is the problem with Uncaught TypeError: jQuery(...).fancybox is not a function?

Question

JavaScript

The problem is as follows
Each time the page is refreshed in the browser, sliders disappear / work:
In the console, it displays the following:

main.js?ver=5:139 Uncaught TypeError: jQuery(...).fancybox is not a function
    at HTMLDocument.<anonymous> (main.js?ver=5:139)
    at i (jquery.js?ver=1.12.4-wp:2)
    at Object.add [as done] (jquery.js?ver=1.12.4-wp:2)
    at a.fn.init.n.fn.ready (jquery.js?ver=1.12.4-wp:2)
    at main.js?ver=5:23

That is, there is an error, then there is no error and the site is displayed normally. How can this be resolved?

Answer 1

In async apparently

async: Load order (whoever loads first will work).