SX OS is no longer supported and fails with updates past v1.4.0. You must migrate to Atmosphere. There is no workaround for SX OS users to get new DLC working.
You cannot mix regions easily on CFW.
Game: One Piece: Pirate Warriors 4
Platform: Nintendo Switch (CFW)
File Format: NSP (base + updates) + DLC unlocks one piece pirate warriors 4 nsp update dlc work