Server Crashing due to an error

[Taio-Holloway]

Hey there! I'll post more info tonight when I can ask the player who experienced the problem, but noticed the server crash twice over the course of 2 and a half hours with this same error message.

[04:52:51] [Server thread/ERROR]: Could not pass event ChunkUnloadEvent to mcMMO v2.2.029
org.bukkit.event.EventException: null
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:310) ~[spigot-api-1.21.4-R0.1-SNAPSHOT.jar:?]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[spigot-api-1.21.4-R0.1-SNAPSHOT.jar:?]
at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:601) ~[spigot-api-1.21.4-R0.1-SNAPSHOT.jar:?]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:588) ~[spigot-api-1.21.4-R0.1-SNAPSHOT.jar:?]
at net.minecraft.world.level.chunk.Chunk.unloadCallback(Chunk.java:625) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.PlayerChunk.lambda$callEventIfUnloading$7(PlayerChunk.java:341) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.PlayerChunkMap$CallbackExecutor.run(PlayerChunkMap.java:171) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.PlayerChunk.a(PlayerChunk.java:429) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.ChunkMapDistance.a(ChunkMapDistance.java:138) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.ChunkProviderServer.s(ChunkProviderServer.java:304) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.ChunkProviderServer$b.B(ChunkProviderServer.java:681) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.ChunkProviderServer.d(ChunkProviderServer.java:300) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.bv(MinecraftServer.java:1307) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.B(MinecraftServer.java:1291) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.util.thread.IAsyncTaskHandler.b(SourceFile:147) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.b(MinecraftServer.java:1248) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.x_(MinecraftServer.java:1258) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.y(MinecraftServer.java:1101) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:329) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]
Caused by: java.lang.NullPointerException: Cannot invoke "it.unimi.dsi.fastutil.objects.ReferenceArrayList.get(int)" because "this.wrapped" is null
at it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet$SetIterator.next(ReferenceOpenHashSet.java:520) ~[fastutil-8.5.15.jar:?]
at net.minecraft.server.level.ChunkMapDistance.a(ChunkMapDistance.java:137) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.ChunkProviderServer.s(ChunkProviderServer.java:304) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.ChunkProviderServer.c(ChunkProviderServer.java:261) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.ChunkProviderServer.a(ChunkProviderServer.java:160) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.world.level.World.a(World.java:299) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at org.bukkit.craftbukkit.v1_21_R3.CraftWorld.getChunkAt(CraftWorld.java:228) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at org.bukkit.craftbukkit.v1_21_R3.CraftChunk.getEntities(CraftChunk.java:127) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at com.gmail.nossr50.listeners.ChunkListener.onChunkUnload(ChunkListener.java:17) ~[?:?]
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103) ~[?:?]
at java.base/java.lang.reflect.Method.invoke(Method.java:580) ~[?:?]
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[spigot-api-1.21.4-R0.1-SNAPSHOT.jar:?]
... 19 more
[04:52:51] [Server thread/ERROR]: Encountered an unexpected exception
java.lang.NullPointerException: Cannot invoke "it.unimi.dsi.fastutil.objects.ReferenceArrayList.get(int)" because "this.wrapped" is null
at it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet$SetIterator.next(ReferenceOpenHashSet.java:520) ~[fastutil-8.5.15.jar:?]
at net.minecraft.server.level.ChunkMapDistance.a(ChunkMapDistance.java:137) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.ChunkProviderServer.s(ChunkProviderServer.java:304) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.ChunkProviderServer$b.B(ChunkProviderServer.java:681) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.ChunkProviderServer.d(ChunkProviderServer.java:300) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.bv(MinecraftServer.java:1307) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.B(MinecraftServer.java:1291) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.util.thread.IAsyncTaskHandler.b(SourceFile:147) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.b(MinecraftServer.java:1248) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.x_(MinecraftServer.java:1258) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.y(MinecraftServer.java:1101) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:329) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]

[nossr50]

I'm not sure what to make of this, do you have any other plugins that are potentially doing things during chunk load and unload events?

[Taio-Holloway]

Sorry, I didn't notice your reply until now!!! Here is a list of all the plugins on the server at the moment:
-EssentialsX
-EssentialsX Chat
-EssentialsX Protect
-EssentialsX Spawn
-LuckPerms
-Worldedit
-Worldguard

I also just recently got this error as well, which seems related but now doesn't reference MCMMO, so it may be another plugin interfering, or an issue with this version of Spigot:

[Worker-Main-26/ERROR]: Failed to schedule load callback for chunk [-10, 14]
java.util.concurrent.CompletionException: java.lang.OutOfMemoryError: Java heap space
at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:315) ~[?:?]
at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:320) ~[?:?]
at java.base/java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:722) ~[?:?]
at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:510) ~[?:?]
at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2179) ~[?:?]
at net.minecraft.server.level.GenerationChunkHolder.a(SourceFile:242) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.GenerationChunkHolder.a(SourceFile:106) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at java.base/java.util.concurrent.CompletableFuture.uniHandle(CompletableFuture.java:934) ~[?:?]
at java.base/java.util.concurrent.CompletableFuture$UniHandle.tryFire(CompletableFuture.java:911) ~[?:?]
at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:510) ~[?:?]
at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1773) ~[?:?]
at net.minecraft.server.level.LightEngineThreaded.f(SourceFile:190) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.server.level.LightEngineThreaded.h(SourceFile:163) ~[spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.SystemUtils.a(SourceFile:296) [spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.util.thread.AbstractConsecutiveExecutor.f(SourceFile:50) [spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at net.minecraft.util.thread.AbstractConsecutiveExecutor.run(SourceFile:62) [spigot-1.21.4-R0.1-SNAPSHOT.jar:4418-Spigot-aa7842e-fa10c50]
at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1423) [?:?]
at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:387) [?:?]
at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1312) [?:?]
at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1843) [?:?]
at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1808) [?:?]
at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:188) [?:?]
Caused by: java.lang.OutOfMemoryError: Java heap space

Edit: Actually, could this issue be caused by not having enough allocated server RAM? The server is running on 6GB, but this error seems to correlate to a lack of RAM. I would've thought 6GB would be enough for a pretty basic server with no more than 7 players though, so unsure.