[Languages] Checkout page switches back to another language after a few seconds

Hi,

Have a issue with the checkout page. The default language for this website is German, and on the checkoutpage on the bottom, by order total and shipping, it shows first the German language and after a few seconds (when loading is finished) it switches back to Dutch (see attachment). I have the same with the Woocommerce checkout widget in the header. Sometimes it is in German, sometimes it is in English.

Maybe something is going wrong because this site is a copy of the Dutch version, but it changed everything automatically into German (de_DE), except on the checkout-page, by the total order and shipping part, and as said the Woocommerce checkout widget in the header.

Thanks!

Regards,

rubies