Running 17w06a on a windows 7 computer in creative mode around X:-2000, Z:-2000, I noticed that when I unloaded and then loaded a chunk to make TNT explode (glitched out), leads holding two animals to fence posts instead acted as though they had been tied at 0,0 and somehow had got that far still attached. The bugged-out lead went through hillsides, water etc.

Steps to reproduce:
1. Tie two animals to two fence posts around the coordinates -2000,100,-2000.
2. Leave the chunks and walk away until the chunks are completely unloaded.
3. Head back to the fence posts and then travel beyond.
4. Turn around and go back to the fence posts. These will still have the lead texture tied onto them, but the actual lead itself will point to 0,0