Short explanation:
The translator taking care of spanish could only commit to translating a previous version, so content since then is missing translation.
Long explanation:
Italian is the only language that is completely (or almost completely) translated up to the newest version (The game page lists what versions which languages are translated up to). If I recall correctly spanish is only translated up to the cart scene. Translation is on a volunteer-basis, so this sort of thing will happen.
Also, when I make spelling corrections or changes on english strings, the translations usually get broken.