Mobs disappearing once put through nether portal

This will make the game lose a lot of ways to play.

 it may make a part of players lose their ways of games*😞*

I mean this is...this bug will actually ruin all the hard works we’ve done as BE players on the development of mob tower😞. No doubt that all BE players are hoping Mojang would actually pay attention to this bug and fix it soon.

这个bug将绝对会毁掉BE玩家一切对刷怪塔的研究成果。毋庸置疑，所有的BE玩家都在迫切地等待Mojang这个bug的修复，并希望Mojang能够重视。

Does this happen to mobs that have their persistence set? (tempted, name-tagged, tamed, bred, etc)

It does.

Affects Win 10 too (persistence). Also is random which makes it hard to track. You can send two villagers through ok, but send another set later and one or more will despawn/vanish randomly. Have also had existing name-tagged villagers despawn in base after returning from Nether, but again this is random. A temporary fix is that I always save game before sending through mobs/going exploring new Nether biomes - and reload if I lose any. Not perfect but ok as we are in Beta...

I have the experience of the mobs being in limbo. Adding a 4th mob into portal respawned the mobs and dropped the boats I used. This was after saving and assuming they were lost. Apparently they are stuck in between the 2 portals and have not actually despawned.

This seems like a cause for a potential memory leak if what Kris Beauchamp said is the case.

I am on Bedrock Dedicated Server Linux 1.16 with the same issue. It doesn't always happen, but it often does.

I see there are numerous reports of this across the 1.16 betas that are marked as duplicate and linked to this case.

I have just experienced this for the 3rd time in 2 days with mine arts and villagers when trying to bring them back to my overworked tradehall.

1.16 XB1X with latest dedicated server software

Thiss happening to my drowned farm. They go through the portals and disappear. The tutorial said it was about 500 drowneds an hour 

I'm having the same problem in my drowned farm, but only when it runs on simulation distance 10. When I reduce the simulation distance to 4, nothing despawns!

This appears to be the same issue that was reported in MCPE-22340. That ticket was closed in a bulk resolve due to not being updated.

New duplicate report MCPE-101972 corroborates Peter Schinko's statment above that this only occurs on simulation distance 6 and higher, and does not occur on simulation distance 4. I wonder if it might be related to how the game determines a "simulation edge" chunk, i.e. perhaps it treats the chunk where the exit portal is located as a simulation edge on its first tick b/c the chunks around have not loaded yet, and then it applies simulation edge despawning rules to everything that comes out of the portal?

Update: I am 99% sure that this is indeed what is happening. The attached test world,

can be used to demonstrate this. (It contains the beginnings of a drowned farm I was designing and has 332 mobs in limbo.)

Steps to reproduce

1. Load the test world. It is on sim6.

2. Go through the portal. There will be no mobs in the nether.

3. Re-import a clean copy of the test world.

4. Change the world to sim4.

5. Load the world.

6. Go through the portal. There will be hundreds of drowned in the nether.

7. Re-import a clean copy of the test world again. Leave it on sim6.

8. Use the spawn egg to spawn a drowned.

9. Go through the portal. There will be one drowned--the one that has persistence b/c it was spawned with a spawn egg.

Expected results

Each time you load the world and go through the portal, there will be hundreds of drowned.

Actual results

On sim6 and above, only mobs with persistence load when travelling through the portal, and the rest despawn.

Note

Unfortunately, this can't explain the original report that villagers were disappearing when sent going through a portal, and it wouldn't explain reports of tamed animals and name-tagged mobs never coming out of a portal either. If anyone can reproduce those scenarios, it would be great to get a test world that we can examine.

(UPDATE: This repro is also tracked separately at MCPE-88322.)

I have reproduced this issue for pets using the following steps. It requires two players. (Possibly a ticking area could work instead of a second player.)

1. Create a nether portal in the overworld at 800 Y 800.

2. Have a second player travel through the portal and keep the nether-side portal within their simulation distance. It should be near 100 Y 100

3. Spawn and tame a parrot, dog, or cat in the overworld.

4. Make sure the pet is not sitting.

5. Push the pet into the portal.

6. Have the second player travel to 800 Y 800 in the nether and observe as first player moves around.

Expected results

The second player sees the pet come out of the portal in the nether. The pet stands still because it's owner is not present.

Actual results

The pet is sent its owner's overworld coordinates in the nether. So if the owner is at Overworld 808 70 808, the pet is sent to 808 70 808 in the nether. When the the second player observes there, they see the pet in the nether track the coordinates of its owner in the overworld (if it has not been killed by being sent to a dangerous place). The result may be easiest to see if you use parrots in a flat world and reverse the dimensions, but it works in either direction with all pets.

Notes

The following scenarios seem to work correctly:

• If a second player is not present to keep the other-side portal loaded, the pet will appear in the portal with the owner when the owner comes through.

• If the pet is sat down before being pushed through the portal, it will appear in the portal in the other dimension when pushed through.

• If the pet is standing up but not pushed through the portal, it will come through the portal with the owner.

I tested my drowned farm in Simulation distance of 6 and they didn't despawn when i went to to kill chamber in the beta 1.16.220.52.

Based on the reported (and confirmed by GinePik above) fix for the nether portal despawn issue in the 1.16.220.52, we will resolve this report as "fixed" when that fix makes it to a release version.

The issue with pets being sent to the wrong coordinates when another player is in the other dimension will continue to be tracked at MCPE-88322.

This is still happening occasionally in the 1.16.230.50 beta. Tested by sending naturally spawned mobs thru a portal to the nether on sim 6.

@silentsisperer: could you provide more precise steps to reproduce?

I don't think it's the same problem. I have found mobs (most of the time in my experience) reappear from portals used by the player and otherwise disappear. See MCPE-116572 which differs in a few details from present issue.

Niels Peter Rasmussen: (replying here rather than MCPE-116572 b/c that was resolved as a duplicate)
I tested what I think you mean, and found that non-persistent mobs do not necessarily despawn if you go through a different portal. They despawn if you go through a portal that puts you far enough from the portal where the mobs come out that they are in instant despawn chunks or beyond the instant despawn radius on sim4. Also, if you come out of a portal more than 32 blocks from where the mobs come out then they will be subject to the random despawn timer. Those outcomes are just due to the despawn mechanics working as intended.

Possibly affects 1.18.2. Tested on sim 4 singleplayer by sending naturally spawned mobs and other entities through a portal. When the player goes to the nether, all the naturally spawned mobs are gone but other entities such as items and spawn egg mobs are there. The portal is already within sim distance when the player enters the nether, and the coordinates of the portals are correct. The naturally spawned mobs can occasionally load properly, but I haven’t found a cause for it.

Edit: the y coordinates of the nether side portal were about 50 higher than the overworld side, after lowering it to the same y level the naturally spawn mobs did load correctly. 

Kimowin: please create a new report for the specific case you can reproduce.