Hello !
I don't know if this is a bug or if it is intented, but mobs (hostile and passive) are spawning on the roof of the box.
(it's maybe because I use mods and it broke something, I don't know... also I love your mod 3 )
Have a good day/evening/night !

May be other mods. I still disabled the mob spawning just to make sure no mobs will spawn :) (Will roll out with the next update)