Contradiction with Exodus 34:1
In Exodus, God commands Moses to chisel out stone tablets and write on them, which contrasts Joshua 8:32 where Joshua writes on stones himself.
Exodus 34:1: And the LORD said unto Moses, Hew thee two tables of stone like unto the first: and I will write upon [these] tables the words that were in the first tables, which thou brakest.
Contradiction with Deuteronomy 11:20
Here, the Israelites are instructed to write God's words on doorposts and gates, whereas in Joshua 8:32, Joshua writes the law on stones specifically.
Deuteronomy 11:20: And thou shalt write them upon the door posts of thine house, and upon thy gates:
Contradiction with Hebrews 8:10
This verse speaks of God writing His laws in the hearts and minds, differing from Joshua 8:32 where the law is inscribed on physical stones.
Hebrews 8:10: For this [is] the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people: [put: Gr. give] [in: or, upon]
Contradiction with 2 Corinthians 3:3
Paul talks about the law being written on human hearts, not on tablets of stone like in Joshua 8:32.
2 Corinthians 3:3: [Forasmuch as ye are] manifestly declared to be the epistle of Christ ministered by us, written not with ink, but with the Spirit of the living God; not in tables of stone, but in fleshy tables of the heart.