Contradiction with Matthew 5:1
In this verse, Jesus is depicted as actively seeking a large audience to teach, in contrast to Matthew 13:53, where Jesus concludes His teachings.
Matthew 5:1: And seeing the multitudes, he went up into a mountain: and when he was set, his disciples came unto him:
Contradiction with Matthew 14:23
This verse illustrates Jesus seeking solitude to pray after teaching, which is a different action compared to Matthew 13:53, where He simply ends His parables without described further actions.
Matthew 14:23: And when he had sent the multitudes away, he went up into a mountain apart to pray: and when the evening was come, he was there alone.
Contradiction with John 18:20
Jesus claims to have always taught openly to the world, while Matthew 13:53 ends His specific parable teachings to the crowd, contrasting the claim of continuous openness.
John 18:20: Jesus answered him, I spake openly to the world; I ever taught in the synagogue, and in the temple, whither the Jews always resort; and in secret have I said nothing.