Wasn't able to really nail down what appears to be causing this one, but when carring the blue cube towards the portal in world 11 the world seems to unload around me. I was able to repoduce this a couple times with this same method of:
- Grabbing the cube from the tree
- Entering the door with the cube
- Immediately leaving the door and giving myself some distance
- Return to the door and I would be sent to oblivion
Here's a recording of one of my attempts (start at 1:00):