Translations at checkout page

Hi, I have a problem at my site:
https://www.ludobooks.com

When I put some product in the cart and go to checkout, some billing and shipping fields are shown in English, while other in the local language (Spanish). I can even see when loading the checkout page that they are initially show in the local language, but when loading ends, they get translated again into English.

I’m using woocommerce + polylang + hyyan woocommerce polylang integration + multi currency

If I deactive polylang + hyyan woocommerce polylang integration, it still happens.
But as soon as I deactivate Multi currency plugin, then it doesn’t happen, and all the fields are shown in Spanish.

I can’t figure out the problem, I need your help!

Thanks!
Miguel Angel