A good translator must not only know the language from which he is translating, but also the subject matter. Indeed, expertise in the latter is the more important of the two.
I have been re-reading Jean Piaget's Psychology and Epistemology: Toward a Theory of Knowledge (Viking, 1971, tr. Arnold Rosin). As a marginalium of mine from the autumn of 1972 indicates, the following sentence involves a mis-translation: "In the case of a priori forms, the analysis of facts is more delicate, for it is not enought to analyze the subjects' consciences but also their previous conditions." (p. 5, emphasis added)
In some languages, French being one of them, the word for conscience and the word for consciousness is the same: conscience (in French) Someone versed in philosophy or psychology would know from the context that Piaget is talking about consciousness, not conscience. A competent translator translates the sense, not the word. The sense, however, depends on the context: first the sentence, then the wider contexts (paragraph, etc.)
Translation requires understanding. The notion that translating machines understand anything is preposterous.