When any player goes near a location in Atum2: the game crashes.
-2329.14, y=74.86, z=3608.36]
Seed: [-2263577824371911604]

Appears to be trying to cancel a spawn event that can't be cancelled.

---- Minecraft Crash Report ----
// I bet Cylons wouldn't have this problem.

Time: 9/16/21 10:38 AM
Description: Exception ticking world

java.lang.UnsupportedOperationException: Attempted to call Event#setCanceled() on a non-cancelable event of type: net.minecraftforge.event.entity.living.LivingSpawnEvent.CheckSpawn
at net.minecraftforge.eventbus.api.Event.setCanceled(Event.java:95) ~[eventbus-4.0.0.jar:?] {}
at com.teammetallurgy.atum.misc.event.AtumEventListener.checkSpawn(AtumEventListener.java:237) ~[atum:1.16.5-2.2.7] {re:classloading}
at net.minecraftforge.eventbus.ASMEventHandler_633_AtumEventListener_checkSpawn_CheckSpawn.invoke(.dynamic) ~[?:?] {}
at net.minecraftforge.eventbus.ASMEventHandler.invoke(ASMEventHandler.java:85) ~[eventbus-4.0.0.jar:?] {}
at net.minecraftforge.eventbus.EventBus.post(EventBus.java:302) ~[eventbus-4.0.0.jar:?] {}
at net.minecraftforge.eventbus.EventBus.post(EventBus.java:283) ~[eventbus-4.0.0.jar:?] {}
at net.minecraftforge.event.ForgeEventFactory.canEntitySpawn(ForgeEventFactory.java:201) ~[forge:?] {re:mixin,pl:runtimedistcleaner:A,re:classloading,pl:runtimedistcleaner:A}
at net.minecraftforge.common.ForgeHooks.canEntitySpawn(ForgeHooks.java:1179) ~[forge:?] {re:classloading}
at net.minecraft.world.spawner.WorldEntitySpawner.func_234966_a_(WorldEntitySpawner.java:172) ~[?:?] {re:classloading}
at net.minecraft.world.spawner.WorldEntitySpawner.func_234967_a_(WorldEntitySpawner.java:124) ~[?:?] {re:classloading}
at net.minecraft.world.spawner.WorldEntitySpawner.func_234979_a_(WorldEntitySpawner.java:110) ~[?:?] {re:classloading}
at net.minecraft.world.server.ServerChunkProvider.func_241099_a_(ServerChunkProvider.java:364) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at java.util.ArrayList.forEach(ArrayList.java:1257) ~[?:1.8.0_212] {}
at net.minecraft.world.server.ServerChunkProvider.func_217220_m(ServerChunkProvider.java:351) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.world.server.ServerChunkProvider.func_217207_a(ServerChunkProvider.java:326) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.world.server.ServerWorld.func_72835_b(ServerWorld.java:333) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:APP:abnormals_core.mixins.json:ServerWorldMixin,pl:mixin:A,pl:runtimedistcleaner:A}
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:851) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:291) ~[?:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:787) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:642) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.server.MinecraftServer.func_240783_a_(MinecraftServer.java:232) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212] {}

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Server thread
Stacktrace:
at net.minecraftforge.eventbus.api.Event.setCanceled(Event.java:95) ~[eventbus-4.0.0.jar:?] {}
at com.teammetallurgy.atum.misc.event.AtumEventListener.checkSpawn(AtumEventListener.java:237) ~[atum:1.16.5-2.2.7] {re:classloading}
at net.minecraftforge.eventbus.ASMEventHandler_633_AtumEventListener_checkSpawn_CheckSpawn.invoke(.dynamic) ~[?:?] {}
at net.minecraftforge.eventbus.ASMEventHandler.invoke(ASMEventHandler.java:85) ~[eventbus-4.0.0.jar:?] {}
at net.minecraftforge.eventbus.EventBus.post(EventBus.java:302) ~[eventbus-4.0.0.jar:?] {}
at net.minecraftforge.eventbus.EventBus.post(EventBus.java:283) ~[eventbus-4.0.0.jar:?] {}
at net.minecraftforge.event.ForgeEventFactory.canEntitySpawn(ForgeEventFactory.java:201) ~[forge:?] {re:mixin,pl:runtimedistcleaner:A,re:classloading,pl:runtimedistcleaner:A}
at net.minecraftforge.common.ForgeHooks.canEntitySpawn(ForgeHooks.java:1179) ~[forge:?] {re:classloading}
at net.minecraft.world.spawner.WorldEntitySpawner.func_234966_a_(WorldEntitySpawner.java:172) ~[?:?] {re:classloading}
at net.minecraft.world.spawner.WorldEntitySpawner.func_234967_a_(WorldEntitySpawner.java:124) ~[?:?] {re:classloading}
at net.minecraft.world.spawner.WorldEntitySpawner.func_234979_a_(WorldEntitySpawner.java:110) ~[?:?] {re:classloading}
at net.minecraft.world.server.ServerChunkProvider.func_241099_a_(ServerChunkProvider.java:364) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at java.util.ArrayList.forEach(ArrayList.java:1257) ~[?:1.8.0_212] {}
at net.minecraft.world.server.ServerChunkProvider.func_217220_m(ServerChunkProvider.java:351) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.world.server.ServerChunkProvider.func_217207_a(ServerChunkProvider.java:326) ~[?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.world.server.ServerWorld.func_72835_b(ServerWorld.java:333) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:APP:abnormals_core.mixins.json:ServerWorldMixin,pl:mixin:A,pl:runtimedistcleaner:A}
-- Affected level --
Details:
All players: 1 total; [ServerPlayerEntity['MacTso'/249, l='ServerLevel[forge-1-16-5-36.2.0]', x=-2329.14, y=74.86, z=3608.36]]
Chunk stats: ServerChunkCache: 2210
Level dimension: atum:atum
Derived: true
Level spawn location: World: (42,88,84), Chunk: (at 10,5,4 in 2,5; contains blocks 32,0,80 to 47,255,95), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 58438641 game time, 54729 day time
Level name: forge-1-16-5-36.2.0
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Level weather: Rain time: 13310 (now: false), thunder time: 53050 (now: false)
Known server brands: forge
Level was modded: true
Level storage version: 0x04ABD - Anvil
Stacktrace:
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:851) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:291) ~[?:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:787) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:642) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.server.MinecraftServer.func_240783_a_(MinecraftServer.java:232) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212] {}

-- System Details --
Details:
Minecraft Version: 1.16.5
Minecraft Version ID: 1.16.5
Operating System: Linux (amd64) version 3.10.0-1062.12.1.el7.x86_64
Java Version: 1.8.0_212, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 141811688 bytes (135 MB) / 913833984 bytes (871 MB) up to 5726797824 bytes (5461 MB)
CPUs: 6
JVM Flags: 6 total; -Xms256M -Xmx6144M -XX:+CMSIncrementalPacing -XX:+CMSClassUnloadingEnabled -XX:MinHeapFreeRatio=5 -XX:MaxHeapFreeRatio=10
ModLauncher: 8.0.9+86+master.3cf110c
ModLauncher launch target: fmlserver
ModLauncher naming: srg
ModLauncher services:
/mixin-0.8.2.jar mixin PLUGINSERVICE
/eventbus-4.0.0.jar eventbus PLUGINSERVICE
/forge-1.16.5-36.2.0.jar object_holder_definalize PLUGINSERVICE
/forge-1.16.5-36.2.0.jar runtime_enum_extender PLUGINSERVICE
/accesstransformers-3.0.1.jar accesstransformer PLUGINSERVICE
/forge-1.16.5-36.2.0.jar capability_inject_definalize PLUGINSERVICE
/forge-1.16.5-36.2.0.jar runtimedistcleaner PLUGINSERVICE
/mixin-0.8.2.jar mixin TRANSFORMATIONSERVICE
/forge-1.16.5-36.2.0.jar fml TRANSFORMATIONSERVICE
FML: 36.2
Forge: net.minecraftforge:36.2.0
FML Language Providers:
[email protected]
minecraft@1
Mod List:
TrashSlot_1.16.3-12.2.1.jar |TrashSlot |trashslot |12.2.1 |DONE |Manifest: NOSIGNATURE
bagofyurting-1.16.4-1.2.0.1.jar |Bag of Yurting |bagofyurting |1.2.0.1 |DONE |Manifest: NOSIGNATURE
jei-1.16.5-7.7.1.121.jar |Just Enough Items |jei |7.7.1.121 |DONE |Manifest: NOSIGNATURE
dungeons_mobs-1.16.5-1.0.10.jar |Dungeons Mobs |dungeons_mobs |1.0.10 |DONE |Manifest: NOSIGNATURE
abnormals_core-1.16.5-3.3.0.jar |Abnormals Core |abnormals_core |3.3.0 |DONE |Manifest: NOSIGNATURE
invtweaks-1.16.4-1.0.1.jar |Inventory Tweaks Renewed |invtweaks |1.16.4-1.0.1 |DONE |Manifest: NOSIGNATURE
Waystones_1.16.5-7.6.3.jar |Waystones |waystones |7.6.3 |DONE |Manifest: NOSIGNATURE
HarderBranchMining-1.36.0.8.jar |Harder Branch Mining Mod |harderbranchmining |1.36.0.8 |DONE |Manifest: NOSIGNATURE
NastyMobs-1.16.3-1.0.0.8.jar |Nasty Mobs |nasty |1.0.0.8 |DONE |Manifest: NOSIGNATURE
comforts-forge-1.16.5-4.0.1.1.jar |Comforts |comforts |1.16.5-4.0.1.1 |DONE |Manifest: NOSIGNATURE
citadel-1.8.1-1.16.5.jar |Citadel |citadel |1.8.1 |DONE |Manifest: NOSIGNATURE
alexsmobs-1.12.0.jar |Alex's Mobs |alexsmobs |1.12.0 |DONE |Manifest: NOSIGNATURE
SimpleStorageNetwork-1.16.5-1.4.1.jar |Simple Storage Network |storagenetwork |1.16.5-1.4.1 |DONE |Manifest: 1f:47:ac:b1:61:82:96:b8:47:19:16:d2:61:81:11:60:3a:06:4b:61:31:56:7d:44:31:1e:0c:6f:22:5b:4c:ed
SereneSeasons-1.16.5-4.0.1.121-universal.jar |Serene Seasons |sereneseasons |1.16.5-4.0.1.121 |DONE |Manifest: NOSIGNATURE
OuterEnd-0.2.14.jar |The Outer End |outer_end |0.2.9 |DONE |Manifest: NOSIGNATURE
DungeonCrawl-1.16.5-2.3.2.jar |Dungeon Crawl |dungeoncrawl |2.3.2 |DONE |Manifest: NOSIGNATURE
MutantBeasts-1.16.4-1.1.3.jar |Mutant Beasts |mutantbeasts |1.16.4-1.1.3 |DONE |Manifest: d9:be:bd:b6:9a:e4:14:aa:05:67:fb:84:06:77:a0:c5:10:ec:27:15:1b:d6:c0:88:49:9a:ef:26:77:61:0b:5e
HarderSpawners-1.16.5-1.36.0.16.jar |Harder Spawners Mod |harderspawners |1.36.0.16 |DONE |Manifest: NOSIGNATURE
Hwyla-forge-1.10.11-B78_1.16.2.jar |Waila |waila |1.10.11-B78_1.16.2 |DONE |Manifest: NOSIGNATURE
HostileWaterMonsters-1.36.1.18.jar |Hostile Water Mobs |hostilewatermobs |1.36.1.18 |DONE |Manifest: NOSIGNATURE
traverse-1.16.4-0.4.3.8.jar |Traverse: Reforged |traverse |1.16.4-0.4.3.8 |DONE |Manifest: NOSIGNATURE
forge-1.16.5-36.2.0-universal.jar |Forge |forge |36.2.0 |DONE |Manifest: 22:af:21:d8:19:82:7f:93:94:fe:2b:ac:b7:e4:41:57:68:39:87:b1:a7:5c:c6:44:f9:25:74:21:14:f5:0d:90
SpawnBalanceUtility-1.36.0.11.jar |SpawnBalanceUtility |spawnbalanceutility |1.36.0.11 |DONE |Manifest: NOSIGNATURE
corpse-1.16.5-1.0.5.jar |Corpse |corpse |1.16.5-1.0.5 |DONE |Manifest: NOSIGNATURE
DungeonsArise-1.16.5-2.1.47-release.jar |When Dungeons Arise |dungeons_arise |2.1.47 |DONE |Manifest: NOSIGNATURE
forge-1.16.5-36.2.0-server.jar |Minecraft |minecraft |1.16.5 |DONE |Manifest: NOSIGNATURE
repurposed_structures_forge-3.2.4+1.16.5.jar |Repurposed Structures |repurposed_structures |3.2.4+1.16.5 |DONE |Manifest: NOSIGNATURE
livingthings-1.16.5-1.3.1.jar |Living Things |livingthings |1.16.5 - 1.3.1 |DONE |Manifest: NOSIGNATURE
EasierSleeping-1.16.5-2.0.0.jar |Easier Sleeping |easier_sleeping |2.0.0 |DONE |Manifest: NOSIGNATURE
Beekeeper-1.16.2-1.0.0.4.jar |Beekeeper |bk |1.0.0.4 |DONE |Manifest: NOSIGNATURE
SaveYourPets-1.16.2-1.0.0.5.jar |Save Your Pets |syp |1.0.0.5 |DONE |Manifest: NOSIGNATURE
SpawnerFix-1.16.2-1.0.0.2.jar |Spawner Fix |sf |1.0.0.2 |DONE |Manifest: NOSIGNATURE
dimdungeons-1.13.1.jar |Dimensional Dungeons |dimdungeons |1.16.4-1.13.1 |DONE |Manifest: NOSIGNATURE
curios-forge-1.16.5-4.0.5.3.jar |Curios API |curios |1.16.5-4.0.5.3 |DONE |Manifest: NOSIGNATURE
Atum-1.16.5-2.2.7.jar |Atum 2 |atum |1.16.5-2.2.7 |DONE |Manifest: NOSIGNATURE
collective-1.16.5-2.64.jar |Collective |collective |2.64 |DONE |Manifest: NOSIGNATURE
StorageDrawers-1.16.3-8.3.0.jar |Storage Drawers |storagedrawers |8.3.0 |DONE |Manifest: NOSIGNATURE
Regrowth-1.16.4-1.16.5-1.35.0.22.jar |Regrowth Mod |regrowth |1.16.5-1.35.0.22 |DONE |Manifest: NOSIGNATURE
RedstoneMagic-1.16.4-1.16.5-1.4.0.36.jar |Redstone Magic |redstonemagic |1.16.5-1.4.0.36 |DONE |Manifest: NOSIGNATURE
HappyTrails-1.16.5-1.36.0.8.jar |Happy Trails Mod |happytrails |1.16.5-1.36.0.8 |DONE |Manifest: NOSIGNATURE
TheAbyss2 1.9.7 1.16.5.jar |TheAbyss |theabyss |1.9.7 |DONE |Manifest: NOSIGNATURE
sleepsooner_1.16.5-2.5.jar |Sleep Sooner |sleepsooner |2.5 |DONE |Manifest: NOSIGNATURE
HarderNaturalHealing-1.36.0.6.jar |Harder Natural Healing Mod |hardernaturalhealing |1.36.0.6 |DONE |Manifest: NOSIGNATURE
Quick Harvest-1.16.5-1.4.0.jar |Quick Harvest |quickharvest |1.4.0 |DONE |Manifest: NOSIGNATURE
orcinusscaves-1.3.jar |Orcinus's Cavern |cavern |{1.2.0} |DONE |Manifest: NOSIGNATURE
TA2 beginning 1.0.9 1.16.5.jar |[Add-on] The Abyss: The Beginn|thebeginning |1.0.9 |DONE |Manifest: NOSIGNATURE
HarderFarther-1.16.5-1.36.0.6.jar |Harder Farther Mod |harderfarther |1.36.0.6 |DONE |Manifest: NOSIGNATURE
CodeChickenLib-1.16.5-4.0.3.434-universal.jar |CodeChicken Lib |codechickenlib |4.0.3.434 |DONE |Manifest: 31:e6:db:63:47:4a:6e:e0:0a:2c:11:d1:76:db:4e:82:ff:56:2d:29:93:d2:e5:02:bd:d3:bd:9d:27:47:a5:71
EnderStorage-1.16.5-2.8.0.168-universal.jar |EnderStorage |enderstorage |2.8.0.168 |DONE |Manifest: 31:e6:db:63:47:4a:6e:e0:0a:2c:11:d1:76:db:4e:82:ff:56:2d:29:93:d2:e5:02:bd:d3:bd:9d:27:47:a5:71
SpeakerMod-1.36.0.5.jar |SpeakerMod |speakermod |1.36.0.5 |DONE |Manifest: NOSIGNATURE
Crash Report UUID: 49ecb25c-91af-44bf-bf37-55e7eb182d5d
Player Count: 1 / 60; [ServerPlayerEntity['MacTso'/249, l='ServerLevel[forge-1-16-5-36.2.0]', x=-2329.14, y=74.86, z=3608.36]]
Data Packs: vanilla, mod:harderbranchmining, mod:nasty, mod:mutantbeasts (incompatible), mod:harderspawners (incompatible), mod:hostilewatermobs (incompatible), mod:forge, mod:spawnbalanceutility (incompatible), mod:dungeons_arise, mod:easier_sleeping, mod:bk, mod:sf, mod:dimdungeons, mod:curios, mod:atum, mod:collective, mod:regrowth, mod:redstonemagic (incompatible), mod:hardernaturalhealing (incompatible), mod:harderfarther, mod:speakermod (incompatible), mod:dungeoncrawl, mod:sleepsooner, mod:citadel (incompatible), mod:alexsmobs, mod:cavern, mod:bagofyurting (incompatible), mod:abnormals_core, mod:outer_end, mod:codechickenlib (incompatible), mod:enderstorage (incompatible), mod:storagedrawers (incompatible), mod:repurposed_structures, mod:jei, mod:corpse, mod:livingthings, mod:trashslot (incompatible), mod:dungeons_mobs (incompatible), mod:sereneseasons, mod:happytrails, mod:waila, mod:traverse (incompatible), mod:waystones (incompatible), mod:storagenetwork, mod:quickharvest, mod:syp, mod:comforts, mod:invtweaks (incompatible), mod:theabyss, mod:thebeginning
Is Modded: Definitely; Server brand changed to 'forge'
Type: Dedicated Server (map_server.txt)

May just need a try/catch here :
Or may need to test if the event is cancellable before trying to cancel it.

java.lang.UnsupportedOperationException: Attempted to call Event#setCanceled() on a non-cancelable event of type: net.minecraftforge.event.entity.living.LivingSpawnEvent.CheckSpawn
at net.minecraftforge.eventbus.api.Event.setCanceled(Event.java:95) ~[eventbus-4.0.0.jar:?] {}
at com.teammetallurgy.atum.misc.event.AtumEventListener.checkSpawn(AtumEventListener.java:237) ~[atum:1.16.5-2.2.7] {re:classloading}

It looks like you fixed this issue with the new patch so I'm closing this!

I guess it was assassins in spawners in the large stand alone buildings.