Contradiction with Judges 1:18
This verse mentions Judah and captures Gaza, Ashkelon, and Ekron, which contradicts the presence of the Cherethites/Philistines as conquered by David in 1 Samuel 30:14.
Judges 1:18: Also Judah took Gaza with the coast thereof, and Askelon with the coast thereof, and Ekron with the coast thereof.
Contradiction with Joshua 13:2-3
It lists territories including the land of the Philistines and Geshurites which were not totally conquered by Israelites, conflicting with the complete conquest implied in 1 Samuel 30:14.
Joshua 13:2-3: This [is] the land that yet remaineth: all the borders of the Philistines, and all Geshuri,
Contradiction with 1 Samuel 27:8
David attacks regions including the Geshurites and Amalekites as allies, contradictory to the exclusive portrayal of Amalekites in 1 Samuel 30:14.
1 Samuel 27:8: And David and his men went up, and invaded the Geshurites, and the Gezrites, and the Amalekites: for those [nations were] of old the inhabitants of the land, as thou goest to Shur, even unto the land of Egypt. [Gezrites: or, Gerzites]
Contradiction with 2 Samuel 8:18
Benaiah is over the Cherethites and Pelethites, indicating they were servants rather than enemies, which conflicts with the portrayal of them as adversaries in 1 Samuel 30:14.
2 Samuel 8:18: And Benaiah the son of Jehoiada [was over] both the Cherethites and the Pelethites; and David's sons were chief rulers. [chief rulers: or, princes]
Contradiction with Zephaniah 2:5
Prophesies destruction against the Cherethites by God, predicting a future event rather than a past event like the raid in 1 Samuel 30:14.
Zephaniah 2:5: Woe unto the inhabitants of the sea coast, the nation of the Cherethites! the word of the LORD [is] against you; O Canaan, the land of the Philistines, I will even destroy thee, that there shall be no inhabitant.