server logs - Exception Ticking World error precursor?

[20:28:43] [Server thread/ERROR]: Encountered an unexpected exception
net.minecraft.server.v1_10_R1.ReportedException: Exception ticking world
	at net.minecraft.server.v1_10_R1.MinecraftServer.D(MinecraftServer.java:794) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.DedicatedServer.D(DedicatedServer.java:400) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.MinecraftServer.C(MinecraftServer.java:668) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.MinecraftServer.run(MinecraftServer.java:567) [spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_111]
Caused by: java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901) ~[?:1.8.0_111]
	at java.util.ArrayList$Itr.next(ArrayList.java:851) ~[?:1.8.0_111]
	at net.minecraft.server.v1_10_R1.World.a(World.java:2561) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.SpawnerCreature.a(SpawnerCreature.java:122) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.WorldServer.doTick(WorldServer.java:228) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.MinecraftServer.D(MinecraftServer.java:783) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	... 4 more
[20:28:43] [Server thread/ERROR]: 	Cause of unexpected exception was
java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901) ~[?:1.8.0_111]
	at java.util.ArrayList$Itr.next(ArrayList.java:851) ~[?:1.8.0_111]
	at net.minecraft.server.v1_10_R1.World.a(World.java:2561) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.SpawnerCreature.a(SpawnerCreature.java:122) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.WorldServer.doTick(WorldServer.java:228) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.MinecraftServer.D(MinecraftServer.java:783) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.DedicatedServer.D(DedicatedServer.java:400) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.MinecraftServer.C(MinecraftServer.java:668) ~[spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at net.minecraft.server.v1_10_R1.MinecraftServer.run(MinecraftServer.java:567) [spigot-1.10.2-de459a2-51263e9.jar:git-Spigot-de459a2-51263e9]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_111]