Contradiction with Exodus 8:15
Pharaoh hardens his heart and does not heed the signs and wonders, contrary to Exodus 7:23, where he did not even take the event to heart.
Exodus 8:15: But when Pharaoh saw that there was respite, he hardened his heart, and hearkened not unto them; as the LORD had said.
Contradiction with Exodus 8:32
Again, Pharaoh hardens his heart after agreeing to let the people go, contradicting Exodus 7:23 where he disregarded the sign without negotiation.
Exodus 8:32: And Pharaoh hardened his heart at this time also, neither would he let the people go.
Contradiction with Exodus 9:7
Pharaoh investigates the event and hardens his heart, indicating a level of concern not shown in Exodus 7:23.
Exodus 9:7: And Pharaoh sent, and, behold, there was not one of the cattle of the Israelites dead. And the heart of Pharaoh was hardened, and he did not let the people go.
Contradiction with Exodus 9:34
Pharaoh sins and hardens his heart even after the plague is removed, contrasting with Exodus 7:23 where he shows no such engagement.
Exodus 9:34: And when Pharaoh saw that the rain and the hail and the thunders were ceased, he sinned yet more, and hardened his heart, he and his servants.
Contradiction with Exodus 10:1
God reveals He has hardened Pharaoh's heart, differing from Exodus 7:23 where it is implied Pharaoh's heart was inherently indifferent.
Exodus 10:1: And the LORD said unto Moses, Go in unto Pharaoh: for I have hardened his heart, and the heart of his servants, that I might shew these my signs before him: