It looks like the game can't identify a non-vanilla mob. I've tried mobs from all the ones in the attached config file (changed it to a .txt cause github is being iffy about .json).

bhc-drops.txt

Also attached a crash log.

crash-2019-04-11_18.25.22-client.txt

Maybe if it's not intended to work with non-vanilla mobs, you could maybe make it work with non-vanilla ones? :D

That's not a valid Json you sent ...try adding commas you can use jsonLint to check if a Json is valid

Ah. Well sorry to bother you. That did fix it. There were no comma's in the original file and I'm not versed enough in config editing/JSON-ing to realize it needed comma's :D

Consider the issue closed. But maybe leave it for people with the same issue/question 👍

Anybody reading this. You need to add comma's after each entity you add :D

No it's perfectly fine the bug scared me for like a brief sec then i lol'd a lil when I saw the JSON it's easy once you learn it lol good luck and lemme know if you find anymore bugs.