Update replaced previously loaded chunks

Please provide copies of the world from before and after the update.

OK, how do I do that?  I've tried making a copy of the world file manually, but it keeps saying I don't have permission to move or duplicate the file....  So, erm, what should I do, and how should I do it?

Use the Export button in the world settings, at the bottom of the Game settings, to create a .mcworld file. If it's less than 10 MB, you can attach it to this report. Otherwise, you can upload it to OneDrive and create a sharing link for us to use to download it.

--I have also had a problem like this, and MCPE-149771 describes what might be another example. What might be happening is that no mining or building was ever done in the replaced chunks, so they were considered unmodified chunks and were never written to the world save. Now that world generation has changed, they're still unmodified chunks but now the world generates them differently. There may also be a dependency on the replaced chunks having been first loaded prior to release 1.16. Does that explanation fit your world too?--

Update: I have since learned that the problem I described above is not valid as evidence of a bug, because it only occurred in chunks that I had pruned out of the world in 1.17 using a third-party editor. Mojang can't be responsible for knowing what third-party software did to the world save and therefore can't support the modified world.

Alrighty then, here you go!  First up, the current version, post 1.18.

https://1drv.ms/u/s!AgdPqwZh1adghAS9wBvGdD3gu-Qc?e=3CcgRF

And second, here's the copy of the world from 1.17.1 that was made upon being prompted to do so when first opening the world in 1.18...

https://1drv.ms/u/s!AgdPqwZh1adghAVADgiQqTYguMrt?e=o2HfuW

So, let me know if there is anything else, and I'll see what I can do, Rockatoa, a hoping for a quick fix Brickticks out!

P.S.  Here's another version of the same world, last played in 1.17.1, it's in creative mode, but uses the same world seed and was created in the same version as the ones above, you know, just in case it helps...

https://1drv.ms/u/s!AgdPqwZh1adghAbKmkZKJ_N9uir_?e=CATsFI

Thanks for providing the example worlds. Could you please confirm whether the worlds have been edited using a third party editor at any point?

Additionally, this might be just that the chunks weren't saved beforehand (because they had not been built in) - if this is the case it might be working as intended.

No world editing has occurred.

You missed the implicit second question: Did you mine or build in any of the chunks that were changed unexpectedly?

I honestly don't know, I had been exploring all these chunks in preparation for 1.18, and honestly don't remember which extreme hills I had to use dirt blocks to climb up to get to the top.  Sorry, but I kinda need this fixed regardless, so, help?

When loading Matthew James Riley's backup world I noticed that there are item drops in some of the chunks that are apparently being re-generated. For example, there is mutton and wool at 1112, 64, 409 on top of the red sands or terracotta of the mesa. Now, there is a little two-chunk plains/forest biome a few blocks away that spawns sheep, but the mutton and wool are several blocks into the mesa and are there upon first loading. The sheep must have spawned in that chunk and been killed by the player (or wolf if it was a forest biome) before the 1.18.0 update generated mesa terrain at that spot. This suggests that at least some of the mesa chunks were in fact simulated as a different biome and perhaps visited by the player before the update.

I confirmed that the mutton and wool are there on first loading by making repeat a command block that teleports all entites straigh up to Y = 100 in a fresh load of the backup world, pick-blocking it, and placing a new copy of it down every 50 blocks as I traveled toward the spot. If you travel around the area doing this you will also find seeds in the mesa, and mutton and wool in the desert nearby.

After the most recent update an underwater monument and a nether fortress moved location in one of my world's. Before the update the nether fortress was at 176, ?, -112. But after the update it was at 384, ?, 272...

I don't remember the precise coordinates for the monument, but it's moved over 800 blocks away, at least.

Ps. I collected blaze rods from the previous fortress only to find that when I went to return to get more it'd moved...

@unknown: The presence of "?" instead of a Y coordinate tells me you took this from the output of a /locate command. Release 1.18 completely replaces world generation, including how the locations of generated structures are calculated from the world seed. The /locate command uses this same calculation and therefore also gives different results in 1.18 than it did in 1.17 with the Caves & Cliffs Experiments toggle turned off. You can no longer use /locate to find the positions of structures that were generated before 1.18. Furthermore, the command may tell you a structure is at some location when in fact there's no structure or a different structure there, because the chunks were already generated in 1.17 using the older style world generation.

Although these consequences are undesirable, they cannot be helped and cannot be described as a bug. The only way to prevent this from happening would be to never change world generation, which would mean we could never have new biomes or structures added to the game.

So, any ETA on when this might be fixed, or should I just keep waiting?

Reply from @unknown:
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Thank you for your report!
After consideration, the issue is being closed as Working as Intended.

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