When I clone in a large number of builds at the same time which include signs all over the place, the console starts spamming that message. I've not been able to isolate the exact coordinates for this phenomenon, but it happens usually after a while when playing my new MC map. Since it is an unreleased map I am unable to share the save, but you can see the bug occur in this video: http://youtu.be/ZjN8J0tJrTw This video was made a few snapshots ago, the issue went away for a while but I noticed it again today in 14w33c