Contradiction with Matthew 14:17
Contradiction in the number of loaves mentioned.
Matthew 14:17: And they say unto him, We have here but five loaves, and two fishes.
Contradiction with Mark 6:38
Different description of loaves available for the feeding.
Mark 6:38: He saith unto them, How many loaves have ye? go and see. And when they knew, they say, Five, and two fishes.
Contradiction with Luke 9:13
Different account of available food and logistics for feeding the multitude.
Luke 9:13: But he said unto them, Give ye them to eat. And they said, We have no more but five loaves and two fishes; except we should go and buy meat for all this people.
Contradiction with John 20:1
No direct contradiction, emphasizes a different event unrelated to feeding.
John 20:1: The first [day] of the week cometh Mary Magdalene early, when it was yet dark, unto the sepulchre, and seeth the stone taken away from the sepulchre.