I have corrected the Default_Loot.json file correctly and everything from there is fine.

I'm just wondering how I can get more than around 15 loot spawns per raid? A lot of the boxes have nothing in them.

check the documentation on rb.populate all

make your own loot table and use that

you can do what you want by enabling Allow Duplicate Items, but i wouldn't suggest it until after you've made your own :p

Thanks! :D