When dogs are attached to a fence post by leads, if the post is moved by a piston from far away, the dog will not attach any entity that hurts the player. This does not happen if the lead is broken at a close range where the wolf does not teleport. Rejoining the world will fix this.

Steps to Reproduce:

1. Spawn a wolf, tame it
2. Attach it to a fence post (standing)
3. Stand far enough away from the post so that the wolf can teleport
4. Any way you see fit, detach the lead (can use a piston and redstone, /setblock on the post, etc)
5. Let an entity hurt you (zombie, skeleton, etc)

Expected Result:

The wolf would attack the mob which hurt you after teleporting.

Observed Behavior:

The wolf will not do anything, and the mob will continue to hurt you.

Screenshots/Videos:

wolf_zombie_1-21.mp4