Save here:
to reproduce simply give NPC a backpack with the ‘use this’ command, all required mods included
https://mega.nz/#!kyoRnDLb!c0RkgkLlZvXD0cO8WRrah-DcmRDaA8J6-i9mllJGras
Could be related to the inventory item dropping bugs. See below for more details.