Fields factory not registering that checkbox has been hit

When the customers clicks the checkbox on the webpage and selects an Amount, then when they try adding the product to their basket, a pop-up asks them to “please hit the checkbox”. This indicates that the actions done on the webpage are not sent through without a refresh of the page.

Steps to repeat:
1. Hit checkbox “I understand”
2. Select Amount “1.0 kg”
3. Click “Add to basket”

Page shows pop-up: “Please hit the checkbox” even tho it has been checked. On a second try of adding to cart it works.

The page I need help with: [log in to see the link]