Contradiction with Matthew 17:1
While Luke 9:28 mentions "about an eight days after these sayings," Matthew 17:1 states "after six days," creating a discrepancy in the time frame between the two accounts.
Matthew 17:1: And after six days Jesus taketh Peter, James, and John his brother, and bringeth them up into an high mountain apart,
Contradiction with Mark 9:2
Similar to Matthew, Mark 9:2 also mentions "after six days" as opposed to Luke's "about an eight days after," presenting a contradiction in the duration before the Transfiguration event.
Mark 9:2: And after six days Jesus taketh [with him] Peter, and James, and John, and leadeth them up into an high mountain apart by themselves: and he was transfigured before them.