Ajaxify cart is only working in native language - not in other languages

I followed this guide - and it works very well:
https://community.shopify.com/c/Shopify-Design/Product-pages-Stay-on-the-product-page-after-adding-products-to/m-p/616440

However, it only works when people are visiting my native shop language (Danish).

When they visit the English site on /en/ - it just redirects to the cart page after adding a product to the cart.

I really don’t know what causes this - I hope someone can help.

Preview:

https://puretime.dk/?fts=0&preview_theme_id=124888056004

Choose a wall clock and add to cart - then switch to English language and do the same - to see the difference

I think I found a solution.

Look for:

addToCartFormSelector:         'form[action="/cart/add"]',

Replace with:

addToCartFormSelector:         'form[action*="/cart/add"]',