Words with special characters have dissapeared

I have a problem with my blog https://blog.solaga.fr/

There is some letters with special characters (accents and ñ) which have been replaced by a ?

In this article you can see it: https://blog.solaga.fr/musee-de-malaga-decouvrez-ladn-de-la-ville/

This is pretty weird because it doesn't happen in all the words with special characters, just in some of them.

If someone could help me to find a solution, it would be great! :)