What Jesus promised in John 14:26 was a Paraclete. This Paraclete, both the giver and the gift, is what ensures the ongoing inerrancy of His Church.
Peace be with you.
That's worked out well...
paraklétos
Short Definition: an advocate, comforter, helper, Paraclete
The Holy Spirit was sent as all those but the apostles were told that He would bring to their remembrance. No one else was told that but we also know that the advocate, comforter, and helper were also given to each believer and not just the magesterium nor was the magesterium promised that He would bring to their remembrance.
Acts 15:8 And God, who knows the heart, bore witness by granting them the holy Spirit just as he did us. 9 He made no distinction between us and them, for by faith he purified their hearts.