Stated plainly throughout several end cutscenes, even spoken clearly by voice actors who despite being apparently fluent with the language apparently couldn't be bothered pointing out this grammatical flaw.

First instance is on airship spoken by Alphinaud just after the Garuda fight.
"But first we must needs find out all we can." Both the text and spoken line are wrong.

Several cutscenes after that point also have this same combination of words.