Update from @unknown: Leads break whenever the leash knot and the mob that is leashed to it are in separate chunks, and the chunk where the mob is located gets loaded first. This can happen immediately when opening the world or loading into one dimension from another, or when travelling toward a leashed mob for the first time after loading the world or the dimension.
Steps to reproduce
Open
.
Spawn a pig on the gold block and quickly leash it to the fence post on the other side of the wall. The wall ensures that the leash knot and mob remain in separate chunks for the test.
Travel to the lapis block at X = 72.
Save & quit, then reopen the world.
Travel back to the pig.
Expected result
The pig is still leashed.
Observed result
The pig is not leashed. The lead has dropped as an item and the leash knot is still on the fence post.
This happened in older versions in MCPE as well. Leaving a chunk containing an animal on a lead tied to a fence post and returning results in the lead breaking and animal wanders free. Often, I can witness the animals and mobs "bouncing/ teleporting" from one spot to another when entering the chunk whether they're on a lead or not.
Related issues
is duplicated by
relates to
Attachments
Comments


I recently started having this issue. I had frogs and Allay wandering off, but it hadn't happened with any other mob for me. Still annoying the tie the mobs back up though. Allay are a pain to leash on PE.

I've had a problem with this too. I was bringing a young strider back to the overworld and after a about 10 seconds, it teleported back to the nether and broke the lead i was using. although i'm in the Switch version, i didn't see a post for the switch version.

This is still happening in bedrock 1.19.81

In 1.16 (pre-Caves & Cliffs Part 1), I used to tie up 3 yellow sheep to a singular fence post at the front of my small base. Whenever there was a blackout the lead(s) could break and they wandered off.
In current 1.19.81 when I temporarily tied my horse to that fence post, the lead broke when I loaded up the save (knot remained).
Possibly an issue with incomplete game save data.

Affects 1.20.1

Still happening. A lead occasionally breaks when re-entering the chunk, leaving the lead floating as an item.
Also, the attachment that a lead leaves on the fence is still visible, even though the lead itself has broken.
[media]
The problem also occurs with version 1.20.20.20

Affects 1.20.30.21 preview

Partially fixed, still affects:
•Allay
•Frog
•Camel
•Wolf
•llama
In the world tested
[media]. Evidence video link
If any mobs happen to me, tell me so I will add it

The problem is triggered when the entities move away from lead. The behavior of the frog that causes it to break the leash is its jump, each jump it takes, it moves further away from the leash, but since the leash has not been loaded, it does not make it return, once it has gone far enough and then loads. The chunk where the strap is located will break. The behavior of the allay is to chase the player or an item. If the allay tries to grab an item that is close to it but is tied and the chunk where the leash is located is unloaded, it will cause the allay to move away without anything blocking that movement. Causing that once the strap is loaded it breaks when that chunk is loaded. The behavior of the wolf is that it is angry and tries to kill the llama, which causes that if the strap is not loaded and if the wolf moves far enough away and called by the push this breaks when the belt is loaded.
It affects all entities that are pushed by other entities like the wolf pack pushes pigs while unloading their leash. The solution I would propose is for entities to have anti push while their straps are unloaded and remove their AIs so they don't move while their strap is unloaded.

@Timer RP Happens to sheeps as well. Likely is a problem with anything moving attached to a lead.

Mobs pushing other mobs and breaking their leads as a result is something that happens anywhere. It is not part of this report because it has no essential relationship to reloadIng.
The other examples of breaking still happening when loading are cases where mobs try to move when leashed. These could be considered edge cases of MCPE-47168 as much as this issue. The fix applied to this issue in 1.19.50 makes leads not break only because the knot is unloaded. It was not aimed at leads breaking because the mob moved and the lead could not function properly.
Perhaps a complete fix would require that leash knots be loaded outside of simulation distance. The leash not may not need to be ticked, so long as the leashed mob can detect that the knot is present because it is loaded in memory.