The Bug:
A desync occurs when leads are attached to entities that are just barely out of reach.
Client-side, it appears like a lead is attached to the said entity and will not break no matter how far away you go.
Steps to Reproduce:
Enter creative mode and obtain a lead.
Summon a boat and attach a lead to it.
Fly upwards in the air and as the boat travels downward, quickly detach and reattach the lead to it.
Observed Behavior:
A desync occurs resulting in the lead attaching to the entity client-side, but not server-side.
Expected Behavior:
No desync occurs.
Please describe the issue in text as well, just providing a video with no context is not very good.