Observed on 9/4/20 to 18/4/20 via analytics for 1.14-1.38:
Stacktrace:

java.util.ConcurrentModificationException at java.util.LinkedHashMap$LinkedHashIterator.nextNode(LinkedHashMap.java:711) at java.util.LinkedHashMap$LinkedKeyIterator.next(LinkedHashMap.java:734) at java.util.AbstractCollection.addAll(AbstractCollection.java:343) at bassebombecraft.entity.ai.AiUtils.assignAiGoals(AiUtils.java:149) at bassebombecraft.event.charm.DefaultCharmedMobsRepository.remove(DefaultCharmedMobsRepository.java:55) at bassebombecraft.event.charm.DefaultCharmedMobsRepository.update(DefaultCharmedMobsRepository.java:72) at bassebombecraft.event.charm.CharmedMobEventHandler.handleLivingUpdateEvent(CharmedMobEventHandler.java:56) at net.minecraftforge.eventbus.ASMEventHandler_269_CharmedMobEventHandler_handleLivingUpdateEvent_LivingUpdateEvent.invoke(.dynamic) at net.minecraftforge.eventbus.ASMEventHandler.invoke(ASMEventHandler.java:80) at net.minecraftforge.eventbus.EventBus.post(EventBus.java:258) at net.minecraftforge.common.ForgeHooks.onLivingUpdate(ForgeHooks.java:312) at net.minecraft.entity.LivingEntity.func_70071_h_(LivingEntity.java:1963) at net.minecraft.entity.MobEntity.func_70071_h_(MobEntity.java:274) at net.minecraft.world.server.ServerWorld.func_217479_a(ServerWorld.java:587) at net.minecraft.world.server.ServerWorld$$Lambda$5478/1317007007.accept(Unknown Source) at net.minecraft.world.World.func_217390_a(World.java:684) at net.minecraft.world.server.ServerWorld.func_72835_b(ServerWorld.java:394) at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:829) at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:764) at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:112) at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:622) at java.lang.Thread.run(Thread.java:745) Idkusernames;Windows 10,10.0,amd64;1.8.0_51;1.14.4;28.1.113;20190829.143755;