Background of the issue:
I am trying to fix the Slovak version of my website. I cannot add to cart, and it breaks my page. Link to a page where the issue can be seen: hidden link
Symptoms:
I expected to see the add to cart working. Instead, I got an empty cart and a broken page.
Questions:
Why can't I add to cart on the Slovak version of my website?
What is causing the page to break during checkout?