A player on our server was using an Item Robin to do something with Natura Blueberries being fed through the Item Robin into EnderIO Crafters. The Item Robin seems to have buffered some crazy amount (at least 120k before my client crashed) of blueberries and when the player tried to move the Item Robin it dropped its buffer and the exploding entity count crashed the server.

This is somewhat intended, although for situations like these, I suppose there should be a limit.