3 days ago this started. All the crash reports are similar and are completely random. This is a 1.12 Vanilla Minecraft server that keeps randomly crashing for no reason and I have not been able to figure this out

---- Minecraft Crash Report ----
// I'm sorry, Dave.

Time: 02/07/17 18:58
Description: Exception ticking world

java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.remove(HashMap.java:1451)
at ol.d(SourceFile:198)
at om.d(SourceFile:205)
at net.minecraft.server.MinecraftServer.D(SourceFile:624)
at nx.D(SourceFile:343)
at net.minecraft.server.MinecraftServer.C(SourceFile:560)
at net.minecraft.server.MinecraftServer.run(SourceFile:464)
at java.lang.Thread.run(Thread.java:745)

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

– Head –
Thread: Server thread
Stacktrace:
at java.util.HashMap$HashIterator.remove(HashMap.java:1451)
at ol.d(SourceFile:198)
at om.d(SourceFile:205)

– Affected level –
Details:
Level name: world
All players: 0 total; []
Chunk stats: ServerChunkCache: 573 Drop: 318
Level seed: -8766271026135728136
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: World: (176,64,256), Chunk: (at 0,4,0 in 11,16; contains blocks 176,0,256 to 191,255,271), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 33033769 game time, 23358362 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 89449 (now: false), thunder time: 24760 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
at net.minecraft.server.MinecraftServer.D(SourceFile:624)
at nx.D(SourceFile:343)
at net.minecraft.server.MinecraftServer.C(SourceFile:560)
at net.minecraft.server.MinecraftServer.run(SourceFile:464)
at java.lang.Thread.run(Thread.java:745)

– System Details –
Details:
Minecraft Version: 1.12
Operating System: Linux (amd64) version 3.14.32-xxxx-grs-ipv6-64
Java Version: 1.8.0_111, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 1408518632 bytes (1343 MB) / 3133997056 bytes (2988 MB) up to 3133997056 bytes (2988 MB)
JVM Flags: 5 total; -Xmx3072M -XX:+DisableExplicitGC -XX:+UseConcMarkSweepGC -XX:+AggressiveOpts -XX:MaxGCPauseMillis=30
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Profiler Position: N/A (disabled)
Player Count: 0 / 20; []
Is Modded: Unknown (can't tell)
Type: Dedicated Server (map_server.txt)