Not sure what the issue is but the server has been crashing when people go into the nether and this is the logs when it crashes. Anyone with more experience than me know what is going on/how to fix it?

18.05 03:59:19 [Server] Server thread/ERROR [minecraft/MinecraftServer]: Encountered an unexpected exception
18.05 03:59:19 [Server] INFO net.minecraft.crash.ReportedException: Ticking entity
18.05 03:59:19 [Server] INFO at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:855) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:APP:betterendforge.mixins.json:MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A,pl:runtimedistcleaner:A}
18.05 03:59:19 [Server] INFO at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:291) ~[?:?] {re:classloading,pl:accesstransformer:B}
18.05 03:59:19 [Server] INFO at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:787) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:APP:betterendforge.mixins.json:MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A,pl:runtimedistcleaner:A}
18.05 03:59:19 [Server] INFO at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:642) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:APP:betterendforge.mixins.json:MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A,pl:runtimedistcleaner:A}
18.05 03:59:19 [Server] INFO at net.minecraft.server.MinecraftServer.func_240783_a_(MinecraftServer.java:232) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:APP:betterendforge.mixins.json:MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A,pl:runtimedistcleaner:A}
18.05 03:59:19 [Server] INFO at java.lang.Thread.run(Thread.java:748) [?:1.8.0_211] {}
18.05 03:59:19 [Server] INFO Caused by: java.lang.ClassCastException: net.minecraft.entity.item.ItemEntity cannot be cast to net.minecraft.entity.LivingEntity
18.05 03:59:19 [Server] INFO at com.github.alexthe666.alexsmobs.entity.EntityStradpole.onEntityHit(EntityStradpole.java:297) ~[alexsmobs:1.9.0] {re:classloading}
18.05 03:59:19 [Server] INFO at com.github.alexthe666.alexsmobs.entity.EntityStradpole.onImpact(EntityStradpole.java:252) ~[alexsmobs:1.9.0] {re:classloading}
18.05 03:59:19 [Server] INFO at com.github.alexthe666.alexsmobs.entity.EntityStradpole.func_70071_h_(EntityStradpole.java:219) ~[alexsmobs:1.9.0] {re:classloading}