Overview
When using a spawner minecart with a spider as the spawn potential, it has a chance to spawn a spider jockey, when this happens the game will crash with the error:
"The game crashed whilst exception ticking world
Error: java.lang.IllegalStateException: Entity is already tracked!"
It only effects spawner minecarts not normal spawers
From testing it looks to only be spider jockeys causing it not any other jockeys
Recreate
Summon the following spawner in:
summon spawner_minecart ~ ~ ~ {SpawnCount:20,MinSpawnDelay:50,MaxSpawnDelay:100,MaxNearbyEntities:100,RequiredPlayerRange:16,SpawnData:{id:"minecraft:spider"}}If you summon a few in a give it a minute or 2 the game will crash, when your relog you will see a spider jockey has just been spawned in.
Related issues
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migrated
galaxy_2alex
Thank you for your report!
However, this issue has been temporarily closed as Awaiting Response - this does not mean the report is not valid, we just need more information to verify it.
Please attach the crash report found in [minecraft/crash-reports/crash-<DATE>-client.txt|https://minecrafthopper.net/help/guides/finding-minecraft-data-folder/] here.
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migrated
Hi sorry, completely forgot to add the crash reports first time round they have all been added now:
[media]https://bugs.mojang.com/browse/MC-192296?focusedCommentId=747125&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-747125
suppergerrie2
The same thing happens for striders.
It will happen for all mobs that spawn a rider with it. The entity spawned has `onInitialSpawn` (MCP name) called, which for the strider and spider has a chance of spawning a strider.
Later the spawner minecart adds all passengers of the entity it wants to spawn to the world, but since the spider and strider have already done that it will cause a crash later in the tick when the entities are processed.
migrated
This bug still happens in 20w27a?
boq
Hmm, seems that this bug happened as far as 1.13 (and probably versions before). Though it causes crash only for spawner minecarts (blocks spawners will only cause warning on reload), so probably that's why it was only reported now.
migrated
Fixed in 20w30a