Is the output grammatical or well-formed in the target language? Using an interlingua should be helpful in this regard, because with a fixed interlingua one should be able to write a grammatical mapping to the target language from the interlingua.
Is the output well-structured or grammatically correct according to the conventions of the target language? Leveraging an intermediate language can facilitate creating a translation that adheres to the target language's grammatical norms and expectations.