Contradiction with Deuteronomy 7:22
This verse says the Lord will drive out nations "little by little," which contrasts with Joshua 23:5's implication of complete and quick removal.
Deuteronomy 7:22: And the LORD thy God will put out those nations before thee by little and little: thou mayest not consume them at once, lest the beasts of the field increase upon thee. [put...: Heb. pluck off]
Contradiction with Judges 2:21-23
These verses state that God will no longer drive out the nations, contradicting Joshua 23:5's promise of doing so.
Judges 2:21-23: I also will not henceforth drive out any from before them of the nations which Joshua left when he died:
Contradiction with Joshua 15:63
This verse talks about the Jebusites not being driven out by the children of Judah, indicating a contradiction with the promise of dispossession mentioned in Joshua 23:5.
Joshua 15:63: As for the Jebusites the inhabitants of Jerusalem, the children of Judah could not drive them out: but the Jebusites dwell with the children of Judah at Jerusalem unto this day.
Contradiction with Joshua 13:1-6
God lists the lands still left to possess, contrary to the idea in Joshua 23:5 that he would have already driven the nations out.
Joshua 13:1-6: Now Joshua was old [and] stricken in years; and the LORD said unto him, Thou art old [and] stricken in years, and there remaineth yet very much land to be possessed. [to...: Heb. to possess it]
Contradiction with Judges 1:27-28
The Israelites failed to drive out several Canaanite groups, contradicting the promise in Joshua 23:5.
Judges 1:27-28: 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.
Paradox #1
The potential contradiction or conflict could be the idea of one group taking over another group's land, which might seem morally troubling in terms of fairness and respect for others' rights. It might conflict with modern views on coexistence and respecting different peoples.