Contradiction with 1 Kings 9:20-21
These verses speak of the non-Israelite people that were not completely driven out, contradicting the complete settlement implied in Joshua 21:23.
1 Kings 9:20-21: [And] all the people [that were] left of the Amorites, Hittites, Perizzites, Hivites, and Jebusites, which [were] not of the children of Israel,
Contradiction with Judges 1:27
This verse mentions the Canaanites living among the Israelites, contradicting the notion that they had fully inherited and settled their lands as implied in Joshua 21:23.
Judges 1:27: Neither did Manasseh drive out [the inhabitants of] Bethshean and her towns, nor Taanach and her towns, nor the inhabitants of Dor and her towns, nor the inhabitants of Ibleam and her towns, nor the inhabitants of Megiddo and her towns: but the Canaanites would dwell in that land.
Contradiction with Judges 1:29
Ephraim did not drive out the Canaanites who lived in Gezer, contradicting the completeness of settlement in Joshua 21:23.
Judges 1:29: Neither did Ephraim drive out the Canaanites that dwelt in Gezer; but the Canaanites dwelt in Gezer among them.
Contradiction with Judges 1:33
This verse notes that Naphtali did not entirely drive out the inhabitants, again suggesting incomplete conquest contrary to Joshua 21:23.
Judges 1:33: Neither did Naphtali drive out the inhabitants of Bethshemesh, nor the inhabitants of Bethanath; but he dwelt among the Canaanites, the inhabitants of the land: nevertheless the inhabitants of Bethshemesh and of Bethanath became tributaries unto them.
Contradiction with Judges 2:1-3
God declares He won't drive the nations out, which contradicts the idea presented in Joshua 21:23 that tribes had full settlement and victory.
Judges 2:1-3: And an angel of the LORD came up from Gilgal to Bochim, and said, I made you to go up out of Egypt, and have brought you unto the land which I sware unto your fathers; and I said, I will never break my covenant with you. [angel: or, messenger]