Contradiction with Leviticus 20:17
Contradiction comes as it prescribes punishment for actions similar to those forbidden in Leviticus 18:13, showing inconsistency in enforcement and severity.
Leviticus 20:17: And if a man shall take his sister, his father's daughter, or his mother's daughter, and see her nakedness, and she see his nakedness; it [is] a wicked thing; and they shall be cut off in the sight of their people: he hath uncovered his sister's nakedness; he shall bear his iniquity.