Contradiction with Exodus 28:4
Leviticus 8:7 describes Moses clothing Aaron with the priestly garments, but Exodus 28:4 indicates that God commanded Moses to make these garments for Aaron, not Moses to dress Aaron himself.
Exodus 28:4: And these [are] the garments which they shall make; a breastplate, and an ephod, and a robe, and a broidered coat, a mitre, and a girdle: and they shall make holy garments for Aaron thy brother, and his sons, that he may minister unto me in the priest's office.
Contradiction with Numbers 20:28
Numbers 20:28 describes Moses stripping Aaron of his garments, which contrasts with Leviticus 8:7 where Moses is described as clothing Aaron, showing both the beginning and the end of Aaron's priestly duties.
Numbers 20:28: And Moses stripped Aaron of his garments, and put them upon Eleazar his son; and Aaron died there in the top of the mount: and Moses and Eleazar came down from the mount.