The server files for Crash at position (-606 67 234) can be found here:
https://mega.nz/file/6x8ETAZL#ZV9SLor0RPbHXD2F5xxhwVjZNUm3ac6ItZYKLWon_VQ

---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 15.02.21, 10:12
Description: Exception ticking world

java.util.ConcurrentModificationException
	at java.base/java.util.HashMap$HashIterator.nextNode(HashMap.java:1584)
	at java.base/java.util.HashMap$KeyIterator.next(HashMap.java:1607)
	at aag.a(SourceFile:1007)
	at brx.a(SourceFile:251)
	at brx.a(SourceFile:217)
	at brx.a(SourceFile:291)
	at cea.a(SourceFile:232)
	at ceg$a.a(SourceFile:835)
	at aag.a(SourceFile:1064)
	at aag.ak(SourceFile:1055)
	at aag.a(SourceFile:366)
	at net.minecraft.server.MinecraftServer.b(SourceFile:871)
	at zg.b(SourceFile:312)
	at net.minecraft.server.MinecraftServer.a(SourceFile:811)
	at net.minecraft.server.MinecraftServer.w(SourceFile:670)
	at net.minecraft.server.MinecraftServer.a(SourceFile:257)
	at java.base/java.lang.Thread.run(Thread.java:832)


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

-- Head --
Thread: Server thread
Stacktrace:
	at java.base/java.util.HashMap$HashIterator.nextNode(HashMap.java:1584)
	at java.base/java.util.HashMap$KeyIterator.next(HashMap.java:1607)
	at aag.a(SourceFile:1007)
	at brx.a(SourceFile:251)
	at brx.a(SourceFile:217)
	at brx.a(SourceFile:291)
	at cea.a(SourceFile:232)
	at ceg$a.a(SourceFile:835)
	at aag.a(SourceFile:1064)
	at aag.ak(SourceFile:1055)
	at aag.a(SourceFile:366)

-- Affected level --
Details:
	All players: 1 total; [aah['Kaijobu'/205, l='ServerLevel[giggler_1]', x=-605.50, y=67.00, z=234.50]]
	Chunk stats: ServerChunkCache: 3750
	Level dimension: minecraft:overworld
	Level spawn location: World: (-209,64,-248), Chunk: (at 15,4,8 in -14,-16; contains blocks -224,0,-256 to -209,255,-241), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
	Level time: 110064577 game time, 459 day time
	Level name: giggler_1
	Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
	Level weather: Rain time: 1 (now: false), thunder time: 1 (now: false)
	Known server brands: vanilla, Spigot
	Level was modded: true
	Level storage version: 0x04ABD - Anvil
Stacktrace:
	at net.minecraft.server.MinecraftServer.b(SourceFile:871)
	at zg.b(SourceFile:312)
	at net.minecraft.server.MinecraftServer.a(SourceFile:811)
	at net.minecraft.server.MinecraftServer.w(SourceFile:670)
	at net.minecraft.server.MinecraftServer.a(SourceFile:257)
	at java.base/java.lang.Thread.run(Thread.java:832)

-- System Details --
Details:
	Minecraft Version: 1.16.5
	Minecraft Version ID: 1.16.5
	Operating System: Windows 10 (amd64) version 10.0
	Java Version: 15.0.1, Oracle Corporation
	Java VM Version: OpenJDK 64-Bit Server VM (mixed mode, sharing), Oracle Corporation
	Memory: 3111638936 bytes (2967 MB) / 4294967296 bytes (4096 MB) up to 12884901888 bytes (12288 MB)
	CPUs: 12
	JVM Flags: 3 total; -Xmx12G -Xms4G -XX:+UseG1GC
	Player Count: 1 / 40; [aah['Kaijobu'/205, l='ServerLevel[giggler_1]', x=-605.50, y=67.00, z=234.50]]
	Data Packs: vanilla
	Is Modded: Unknown (can't tell)
	Type: Dedicated Server (map_server.txt)