Contradiction with Judges 7:1
Judges 7:1 mentions Jerubbaal as another name for Gideon, who is not mentioned in 1 Chronicles 2:7 where Achan is referred to as Achar.
Judges 7:1: Then Jerubbaal, who [is] Gideon, and all the people that [were] with him, rose up early, and pitched beside the well of Harod: so that the host of the Midianites were on the north side of them, by the hill of Moreh, in the valley.
Contradiction with Joshua 7:24
Joshua 7:24 describes Achan's punishment, without naming him as Achar, contradicting the name used in 1 Chronicles 2:7.
Joshua 7:24: And Joshua, and all Israel with him, took Achan the son of Zerah, and the silver, and the garment, and the wedge of gold, and his sons, and his daughters, and his oxen, and his asses, and his sheep, and his tent, and all that he had: and they brought them unto the valley of Achor.
Contradiction with Joshua 22:20
Joshua 22:20 recounts Achan's sin against the Lord, but it does not refer to him as Achar, which contradicts the naming in 1 Chronicles 2:7.
Joshua 22:20: Did not Achan the son of Zerah commit a trespass in the accursed thing, and wrath fell on all the congregation of Israel? and that man perished not alone in his iniquity.