Contradiction with Exodus 29:9
Aaron and his sons are given a perpetual priesthood, but Numbers 20:28 describes Aaron's priesthood being transferred to his son, Eleazar.
Exodus 29:9: And thou shalt gird them with girdles, Aaron and his sons, and put the bonnets on them: and the priest's office shall be theirs for a perpetual statute: and thou shalt consecrate Aaron and his sons. [put: Heb. bind] [consecrate: Heb. fill the hand of]
Contradiction with Hebrews 7:23-24
This passage speaks about the permanent priesthood of Jesus, while Numbers 20:28 shows a transition of priesthood from Aaron to Eleazar.
Hebrews 7:23-24: And they truly were many priests, because they were not suffered to continue by reason of death: