Many times, when leaving the loaded chunks to explore or go to another place (the nether, end, another base, etc.) an animal tied to a fencepost via a lead will be freed from the lead, and the lead will be lying on the ground. This seems to happen randomly. I have tested it with: horses, rabbits, cows, sheep, pigs, chickens, and mooshrooms. I have not tested it with wolves or cats.

What I expected to happen:
When I leave an animal tied to a fence, I expect it to stay tied there when I return to the loaded chunk(s).

What actually happened:
When I left the loaded chunk and came back, my animal would sometimes still be lead up the fence, but sometimes would not be lead to the post and the lead would be lying on the ground.

Steps:
1. Spawn in an animal of any kind of animal.
2. Tie it to a fence with a lead.
3. Walk away into a new chunks.
4. Wait about 1-3 minutes.
5. Come back into the chunk with the animal.
6. If it's not untied, repeat the process as many times as needed.