Matthew 16:21-23 21 From that time Jesus began to show his disciples that he must go to Jerusalem and suffer many things from the elders and chief priests and scribes, and be killed, and on the third day be raised. 22And Peter took him aside and began to rebuke him, saying, "Far be it from you, Lord! This shall never happen to you." 23But he turned and said to Peter, "Get behind me, Satan! You are a hindrance to me. For you are not setting your mind on the things of God, but on the things of man."
Very first recorded incident after Jesus supposedly stating that Peter was the rock on which His church would be built and Peter blows it. So much for never erring......
Acts 1: 15-16, 23-26 15In those days Peter stood up among the brothers (the company of persons was in all about 120) and said, 16"Brothers, the Scripture had to be fulfilled, which the Holy Spirit spoke beforehand by the mouth of David concerning Judas, who became a guide to those who arrested Jesus......
23And they put forward two, Joseph called Barsabbas, who was also called Justus, and Matthias. 24And they prayed and said, "You, Lord, who know the hearts of all, show which one of these two you have chosen 25to take the place in this ministry and apostleship from which Judas turned aside to go to his own place." 26And they cast lots for them, and the lot fell on Matthias, and he was numbered with the eleven apostles.
Matthias who?
Galatians 2:11-14 11But when Cephas came to Antioch, I opposed him to his face, because he stood condemned. 12For before certain men came from James, he was eating with the Gentiles; but when they came he drew back and separated himself, fearing the circumcision party. 13And the rest of the Jews acted hypocritically along with him, so that even Barnabas was led astray by their hypocrisy. 14But when I saw that their conduct was not in step with the truth of the gospel, I said to Cephas before them all, "If you, though a Jew, live like a Gentile and not like a Jew, how can you force the Gentiles to live like Jews?"
Peter was wrong. Imagine that.
Christ was not so stupid that He would have protected all church leaders from making errors or misstatements. The Pope could come out tomorrow and state that he thinks that terycarl is the most intelligent person on earth....he would be close to the truth, but nevertheless while being slightly in error, he would not have violated the infallibillity of his office. Only when teaching the world in matters of faith and morals is he protected from error. There is always a human being as head of the church and humans make mistakes, but thusfar there have been no errors in the teachings of the Catholic curch when it comes to matters protected by Jesus' promise.