Server Continues to Stop Randomly.

Hi, So were randomly playing a game of Crundee Craft and the server just randomly stops.
I cannot appear to find a reason or a crash report and the log is just filled with chat from the game.
Please respond as this is happening very much.
Thanks.

Ok, Im not too knowledged in this so ill just paste some of the log from after it crashed here.
[20:59:45] [Server thread/ERROR]: Encountered an unexpected exception
net.minecraft.util.ReportedException: Ticking entity
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:642) ~[MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:334) ~[lt.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547) ~[MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:396) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685) [li.class:?]
Caused by: java.lang.NullPointerException
at net.minecraft.entity.ai.EntityLookHelper.func_75651_a(SourceFile:18) ~[tu.class:?]
at net.minecraft.entity.ai.EntityAIAttackOnCollide.func_75246_d(EntityAIAttackOnCollide.java:93) ~[uq.class:?]
at net.minecraft.entity.ai.EntityAITasks.func_75774_a(SourceFile:103) ~[uj.class:?]
at net.minecraft.entity.EntityLiving.func_70619_bc(EntityLiving.java:540) ~[sw.class:?]
at net.minecraft.entity.EntityLivingBase.func_70636_d(EntityLivingBase.java:1774) ~[sv.class:?]
at net.minecraft.entity.EntityLiving.func_70636_d(EntityLiving.java:367) ~[sw.class:?]
at net.minecraft.entity.monster.EntityMob.func_70636_d(SourceFile:25) ~[yg.class:?]
at net.minecraft.entity.monster.EntityZombie.func_70636_d(EntityZombie.java:217) ~[yq.class:?]
at net.minecraft.entity.EntityLivingBase.func_70071_h_(EntityLivingBase.java:1611) ~[sv.class:?]
at net.minecraft.entity.EntityLiving.func_70071_h_(EntityLiving.java:206) ~[sw.class:?]
at net.minecraft.entity.monster.EntityMob.func_70071_h_(SourceFile:30) ~[yg.class:?]
at net.minecraft.entity.monster.EntityZombie.func_70071_h_(EntityZombie.java:303) ~[yq.class:?]
at net.minecraft.world.World.func_72866_a(World.java:2070) ~[ahb.class:?]
at net.minecraft.world.WorldServer.func_72866_a(WorldServer.java:648) ~[mt.class:?]
at net.minecraft.world.World.func_72870_g(World.java:2034) ~[ahb.class:?]
at net.minecraft.world.World.func_72939_s(World.java:1887) ~[ahb.class:?]
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:489) ~[mt.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:636) ~[MinecraftServer.class:?]
... 4 more
[20:59:45] [Server thread/ERROR]: This crash report has been saved to: /aternos/servers/BlueDragons12/./crash-reports/crash-2017-08-23_20.59.45-server.txt
[20:59:45] [Server thread/INFO]: Stopping server
[20:59:45] [Server thread/INFO]: Saving players
[20:59:45] [Server thread/INFO]: Saving worlds
[20:59:45] [Server thread/INFO]: Saving chunks for level 'world'/Overworld
[20:59:45] [Server thread/INFO]: Saving chunks for level 'world'/Nether
[20:59:45] [Server thread/INFO]: Saving chunks for level 'world'/Moon
[20:59:45] [Server thread/INFO]: Saving chunks for level 'world'/Mars
[20:59:45] [Server thread/INFO]: Saving chunks for level 'world'/Asteroids
[20:59:45] [Server thread/INFO]: Saving chunks for level 'world'/Tropics
[20:59:45] [Server thread/INFO]: Saving chunks for level 'world'/The Last Millenium
[20:59:45] [Server thread/INFO]: Saving chunks for level 'world'/SpectreWorld

Thanks, For the help most of the mods we are using are mods which we have used before with aternos.
This does not occur in other worlds.
I have also submitted a thread post in the mod support section.
Thanks!