Whenever I try to test my game or do a battle, it says "Script referenced an item that does not exist" then closes.
It seems that there is an event in the game(Map, battle or common event), which is using an Item that doesn't exists. If for example you have 50 items in the database, and you make an event that gives the item 35 to the party, and then you change the max number of items in the database to 20, the item 35 will not exist and will make that error. Check all your events, or change the max items number in the database.