---- Minecraft Crash Report -------- Minecraft Crash Report ----// There are four lights! Time: 7/31/21 11:02 PMDescription: Exception ticking world java.util.ConcurrentModificationException at java.util.HashMap$HashIterator.nextNode(Unknown Source) at java.util.HashMap$KeyIterator.next(Unknown Source) at net.minecraft.server.v1_16_R3.WorldServer.notify(WorldServer.java:1227) at net.minecraft.server.v1_16_R3.World.notifyAndUpdatePhysics(World.java:334) at net.minecraft.server.v1_16_R3.World.a(World.java:310) at net.minecraft.server.v1_16_R3.World.setTypeAndData(World.java:225) at net.minecraft.server.v1_16_R3.BlockPiston.a(BlockPiston.java:187) at net.minecraft.server.v1_16_R3.BlockBase$BlockData.a(BlockBase.java:493) at net.minecraft.server.v1_16_R3.WorldServer.a(WorldServer.java:1299) at net.minecraft.server.v1_16_R3.WorldServer.ak(WorldServer.java:1289) at net.minecraft.server.v1_16_R3.WorldServer.doTick(WorldServer.java:346) at net.minecraft.server.v1_16_R3.MinecraftServer.b(MinecraftServer.java:1105) at net.minecraft.server.v1_16_R3.DedicatedServer.b(DedicatedServer.java:355) at net.minecraft.server.v1_16_R3.MinecraftServer.a(MinecraftServer.java:1008) at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:847) at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$0(MinecraftServer.java:164) at java.lang.Thread.run(Unknown Source) A detailed walkthrough of the error, its code path and all known details is as follows:--------------------------------------------------------------------------------------- Head --Thread: Server threadStacktrace: at java.util.HashMap$HashIterator.nextNode(Unknown Source) at java.util.HashMap$KeyIterator.next(Unknown Source) at net.minecraft.server.v1_16_R3.WorldServer.notify(WorldServer.java:1227) at net.minecraft.server.v1_16_R3.World.notifyAndUpdatePhysics(World.java:334) at net.minecraft.server.v1_16_R3.World.a(World.java:310) at net.minecraft.server.v1_16_R3.World.setTypeAndData(World.java:225) at net.minecraft.server.v1_16_R3.BlockPiston.a(BlockPiston.java:187) at net.minecraft.server.v1_16_R3.BlockBase$BlockData.a(BlockBase.java:493) at net.minecraft.server.v1_16_R3.WorldServer.a(WorldServer.java:1299) at net.minecraft.server.v1_16_R3.WorldServer.ak(WorldServer.java:1289) at net.minecraft.server.v1_16_R3.WorldServer.doTick(WorldServer.java:346) Affected level --Details: All players: 1 total; [EntityPlayer['Dream2403'/33007, l='ServerLevel [world_nether] ', x=185.38, y=177.00, z=91.66](Dream2403 at 185.382580271559,177.0,91.66421691179984)] Chunk stats: ServerChunkCache: 3041 Level dimension: minecraft:the_nether Level spawn location: World: (80,64,-176), Chunk: (at 0,4,0 in 5,-11; contains blocks 80,0,-176 to 95,255,-161), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1) Level time: 676891 game time, 776737 day time Level name: world_nether Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: true Level weather: Rain time: 60324 (now: false), thunder time: 108256 (now: false) Known server brands: fabric, Spigot Level was modded: true Level storage version: 0x04ABD - AnvilStacktrace: at net.minecraft.server.v1_16_R3.MinecraftServer.b(MinecraftServer.java:1105) at net.minecraft.server.v1_16_R3.DedicatedServer.b(DedicatedServer.java:355) at net.minecraft.server.v1_16_R3.MinecraftServer.a(MinecraftServer.java:1008) at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:847) at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$0(MinecraftServer.java:164) at java.lang.Thread.run(Unknown Source)