The bug

Teleporting a leash knot does not update its hitbox. The hitbox remains at its old position.
This also happens when directly changing the Pos tag value using the /data command.

How to reproduce

1. Leash an animal to a fence
2. Teleport the leash knot to a second fence

   /teleport @e[type=leash_knot] @s
   

3. Enable hitboxes being shown: F3 + B
   → The hitbox is shown at the old position, hitting it destroys the leash knot

Code analysis

See MC-104582, looks like this might still be accurate.