John 16:13
When the Spirit of truth comes, he will guide you into all the truth;...
Note that this is spoken to the eleven, not to all IHS's followers.
Paul writes, as I said, about the charism and office of teacher. (This implies that some are not teachers and are therefore to be taught.)
It seems not ridiculous to suppose that the Holy Spirit which calls and equips some to be teachers would do so in order for them to teach incorrectly. And there is the promise of "all truth," in the unspecified future, with respect to the time that IHS was speaking.
One might ask which promise of Jesus requires that the Scriptures be infallible and that nothing more be required for Salvation than what could be found in them or proved from them.