Contradiction with Numbers 34:5
This verse contradicts Joshua 15:10 by describing the southern border of the land of Canaan differently, with the border ending at the Salt Sea instead of the location described in Joshua.
Numbers 34:5: And the border shall fetch a compass from Azmon unto the river of Egypt, and the goings out of it shall be at the sea.
Contradiction with Judges 1:18
This verse contradicts Joshua 15:10 because it states that the tribe of Judah captured Ekron, while Joshua 15:10 describes Ekron as part of the land allotted to Judah without mention of its capture.
Judges 1:18: Also Judah took Gaza with the coast thereof, and Askelon with the coast thereof, and Ekron with the coast thereof.