The Meaning of Life, the Universe, and Everything.
It's just that it happens on 2 differently configured computers with each computer using it's own world (Not using the same world as each other). It shouldn't really matter if you'd normally use mine carts differently to how I've used them.
Here's my game config on my computer (The i7). On the other computer I lowered the view distance to Small with negligable impact on the problem.