Contradiction with Galatians 2:6
Galatians describes Paul meeting with the reputed pillars of the church privately, contradicting Acts 21:18 where Paul meets openly with the elders.
Galatians 2:6: But of these who seemed to be somewhat, (whatsoever they were, it maketh no matter to me: God accepteth no man's person:) for they who seemed [to be somewhat] in conference added nothing to me:
Contradiction with Acts 10:28
Peter explains Jews should not associate with Gentiles, which contradicts the meeting with Gentile Paul as described in Acts 21:18.
Acts 10:28: And he said unto them, Ye know how that it is an unlawful thing for a man that is a Jew to keep company, or come unto one of another nation; but God hath shewed me that I should not call any man common or unclean.
Contradiction with James 1:1
James is described as a servant of God, possibly contradicting his role as an elder in Jerusalem in Acts 21:18.
James 1:1: James, a servant of God and of the Lord Jesus Christ, to the twelve tribes which are scattered abroad, greeting.
Contradiction with Acts 11:2-3
Peter is criticized for meeting Gentiles, implying a contradiction where Paul does so openly in Acts 21:18.
Acts 11:2-3: And when Peter was come up to Jerusalem, they that were of the circumcision contended with him,