ConcurrentModificationException in Entity.move caused by Create contraption interaction mixin

[reasure3]

Describe the bug
A ConcurrentModificationException occurs when an entity moves near Create contraptions.
The crash happens inside Create’s EntityContraptionInteractionMixin (create$onMove), during iteration over ContraptionHandler.loadedContraptions.

The exception originates from a synthetic injected mixin method:
Entity.handler$dcc000$create$onMove(Entity.java:7855)

This suggests that the HashMap that stores loaded contraptions is being modified while a stream is iterating over it.

This crash happens even when no Mobile Packages robots are placed in the world.

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To Reproduce
Steps (not deterministic, but consistently reproducible over time):

1. Load into a world with Create contraptions nearby.
2. Walk around or allow entities to move in that area.
3. After some movement, the game/server crashes with a ConcurrentModificationException.

So far, it always occurs during normal entity movement.

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Expected behavior

• Entity movement should not cause a CME.
• Iterating over ContraptionHandler.loadedContraptions should be safe even if modifications occur during the same tick.
• A snapshot copy or concurrent structure may be required.

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Screenshots
N/A

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Desktop (please complete the following information):

• OS: Windows 10
• Forge/NeoForge version: NeoForge 21.1.213
• Minecraft version: 1.21.1
• Create version: 6.0.6
• Create: Mobile Packages version: 0.5.5 (MC 1.21.1)

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Crash log

crash-2025-11-23_22.18.33-server.txt

latest.log

Key excerpt:

java.util.ConcurrentModificationException
at java.base/java.util.HashMap$ValueSpliterator.tryAdvance(HashMap.java:1663)
at java.base/java.util.stream.ReferencePipeline.anyMatch(ReferencePipeline.java:529)
at net.minecraft.world.entity.Entity.handler$dcc000$create$onMove(Entity.java:7855)
at net.minecraft.world.entity.Entity.move(Entity.java:567)

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Additional context

• No Mobile Packages robots exist in the world.
• Crash still occurs, so this is likely not caused by Mobile Packages directly.
• The crash aligns exactly with Create’s EntityContraptionInteractionMixin#create$onMove, especially where the mod checks contraption intersections using: