Crash While leading Llamas (Possibly related to Ender Boxes)

I was leading 2 Llamas around, 1 I had leashed, the other was following the previous one. Then the game crashed.

The crash report mentions Ender Boxes. I had placed two red ones previous to this event, they each had the same contents (17 bones) because I had Ctrl+Middle Clicked one to get the same NBT data and I placed it again.