This bug is already old, there arose some versions, I can not tell which version exactly the bug came, I playing in 14w32c 1.7.10 and the bug is still there. The bug is in a kind of "black hole," an area without any block and insurmountable, if I jump inside I am unable to leave. Currently I am aware of two of these "black holes" in my world, I made a video in which I describe the bug, it's in Portuguese, but there is nothing so important that I speak in video, see the video and you'll understand my bug:

https://www.youtube.com/watch?v=-0upUOvojPc