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MC-304462

Upgrading from version 1.21.11-pre1 may cause a crash

I encountered a crash when loading a world in Minecraft 1.21.11 Pre-Release 2. The crash occurs during chunk loading, specifically when the game tries to update chunks at positions [-12,14] and [-17,14]. The error is a ConcurrentModificationException in the LegacyStructureDataHandler.

Steps to Reproduce:

  1. Have a world that was generated in 1.21.11-pre1 (the seed is 4256825463603229770).

  2. Update to 1.21.11 Pre-Release 2.

  3. Try to load the world.

  4. The game crashes when loading the chunks at the mentioned coordinates.

    image-20251122-133515.png

Attachments

Comments 4

I’m unable to replicate this crash. Please attach a video showcasing this being reproduced in a new world using that seed

This version of my world was created a long time ago and has been gradually upgraded to the latest snapshot. However, I am unable to reproduce it. It might be that the world was damaged during the upgrade process.

However, if I downgrade to 1.21.11-pre1, it will no longer crash.

It no longer appears in 1.21.11-pre3, which is quite strange(

LuoTianyi359

(Unassigned)

Unconfirmed

Crash

1.21.11 Pre-Release 2

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