1. Filename has the spanish title (Cuando Harry encontró a Sally)
2. Library has selected Spanish as language of course, and the localized title option is marked. The library is new, I created a new folder with 3 fims as test for this
3. It founds the film, and it assigns the Spanish description (it's taking the spanish metadata!) and the Spanish poster, good.
4. But somehow it uses the original title instead of the localized.
5. This happens with all the movies, this one is just an example.
You're not doing anything wrong. I just checked the title "When Harry Met Sally" and even for Spanish it's listed on Freebase with the English title:
You can try and use The Movie Database agent as the primary agent for your movies section. With the section language set to Español this gave me the result you are looking for.