JS-Error in single-product.js

Hi

I get this error at the moment and have no idea, how to fix this. jquery is embedded by the theme (skt-white)

Error: ReferenceError: jQuery is not defined
Quelldatei: https://www.wavendo.de/wp-content/plugins/woocommerce/assets/js/frontend/single-product.js
Line: 2

The error appears not every time, so I cant give you a link to proof this.

And what “wc-ajax get_refreshed_fragmentsis”?
Some time product pages load and load and show this in firebug?

I use woocommerce, wpml and table rate shipping plus in newest versions.

Thank you
Tom

https://wordpress.org/plugins/woocommerce/