Contradiction with Luke 22:39
This verse notes that Jesus went out to the Mount of Olives after the Last Supper, suggesting a different sequence than Mark 14:17, which describes the evening when Jesus sat with the twelve.
Luke 22:39: And he came out, and went, as he was wont, to the mount of Olives; and his disciples also followed him.
Contradiction with John 13:30
Describes Judas leaving the meal before Jesus and the disciples eat the Passover, whereas Mark 14:17 indicates Judas remained present with the twelve.
John 13:30: He then having received the sop went immediately out: and it was night.
Contradiction with Matthew 26:20-21
Contradicts Mark 14:17 by implying the presence of only the twelve from the beginning of the meal, unlike the tension that builds through Mark's narrative.
Matthew 26:20-21: Now when the even was come, he sat down with the twelve.