This is something i encountered last time I played through the game, and from what I've seen a number of other people have had this problem as well. Yet no solution or explanation to why or how to solve it.
Usually it happens when trying to devour your companions when they turn hostile due to a decision you made they didn't like or too low influence. I've also seen it apply to Araman when you try to devour him at Eternities end.
Now I'm wondering if anyone who understands how the engine works can give some constructive input on this? If something specific might trigger it that I could avoid. I specifically avoided any official forum, because in my experience they usually remain inactive for months.
Sure I could always spawn the item through the console, but that ruins the immersion a little...