If you have set up multiple languages in your online store, you must set a number of options per language. One of them involves the use of headlines. You must set the headlines per language, because these are images that cannot be translated automatically.

Here's how to fix this. Go to Design > Headlines in the left menu of the back office. When creating the headline you can choose the language of your headline. Do you want the same headline in multiple languages? Then add the headline for each language.