Llamas are not connected or even detached from the fence by itself

Steps to Reproduce:

1. Download and open the attached world (survival)
2. Spawn 10/max llamas then tame and chest them and connect them to fence
3. Spawn 5/<max llamas then tame and chest them and connect them to another fence not far from the previous one
4. Exit the world for ±10 seconds or more/less
5. Go back and look at the differences carefully

Observed Result:
The llamas are not connected or even detached from the fence.

Expected Result:
Llamas remain connected to fences.