Contradiction with Matthew 11:14
John 1:24 mentions those sent by the Pharisees, who questioned John the Baptist about his identity, while Matthew 11:14 refers to Jesus' assertion that John is Elijah, which those questioning did not understand or contradict.
Matthew 11:14: And if ye will receive [it], this is Elias, which was for to come.
Contradiction with John 1:21
In John 1:24, the questioning implies a search for understanding about John the Baptist's role, yet in John 1:21, he explicitly denies being Elijah or the prophet, leading to further confusion about his identity.
John 1:21: And they asked him, What then? Art thou Elias? And he saith, I am not. Art thou that prophet? And he answered, No. [that prophet: or, a prophet?]