Scriptural translations don’t directly fall under the shadow of infallibility (which declares “you must believe this or exclude that”), but could be considered to intersect with it in a few ways. The first is that insofar as the translation would affect one’s understanding of key biblical concepts the authorization of the same translation would amount to endorsing the misreadings, but that is easily sidestepped by the understanding that no matter what the translation it must always be read with the mind of the Church and, at any rate, simply publishing a translation does not amount to imposing it (and to speak infallibly one must intend to bind). On the other hand, were a pope to require that the whole Church use his new translation of Scripture one might view this in light of the theological theory (not established dogma but a very popular idea) of disciplinary infallibility. The theory runs that if the Church were able to command us to do something immoral then our Lord’s promise of Mt 16 would have failed, so whenever the pope lays down law for the universal Church we can trust that - whether or not it mandates an optimal course of action - it cannot, at the very least, be directing us to do anything outright immoral or erroneous. Of course, even under this theory, for God to end a pope’s life rather than allow him to promulgate a bad translation, the translation error would have to pretty unambiguously teach error concerning dogma, so merely doctrinally fuzzy still wouldn’t do the trick.
