Im using forge 2538 and Zombie Awareness1.11.10 and coroutil 1.1.22 under forge2540

[main/FATAL]: Error executing task java.util.concurrent.ExecutionException: java.lang.RuntimeException: A severe problem occurred during the spawning of an entity at (40.2268614321917, 114.870070831177, 45.61953252688285) at java.util.concurrent.FutureTask.report(Unknown Source) ~[?:1.8.0_151] at java.util.concurrent.FutureTask.get(Unknown Source) ~[?:1.8.0_151] at net.minecraft.util.Util.func_181617_a(SourceFile:47) [h.class:?] at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1086) [bib.class:?] at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:397) [bib.class:?] at net.minecraft.client.main.Main.main(SourceFile:123) [Main.class:?] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_151] at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_151] at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_151] at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_151] at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?] at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?] Caused by: java.lang.RuntimeException: A severe problem occurred during the spawning of an entity at (40.2268614321917, 114.870070831177, 45.61953252688285) at net.minecraftforge.fml.common.network.internal.EntitySpawnHandler.spawnEntity(EntitySpawnHandler.java:134) ~[EntitySpawnHandler.class:?] at net.minecraftforge.fml.common.network.internal.EntitySpawnHandler.process(EntitySpawnHandler.java:63) ~[EntitySpawnHandler.class:?] at net.minecraftforge.fml.common.network.internal.EntitySpawnHandler.lambda$channelRead0$0(EntitySpawnHandler.java:55) ~[EntitySpawnHandler.class:?] at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_151] at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_151] at net.minecraft.util.Util.func_181617_a(SourceFile:46) ~[h.class:?] ... 9 more Caused by: io.netty.util.IllegalReferenceCountException: refCnt: 0 at io.netty.buffer.AbstractByteBuf.ensureAccessible(AbstractByteBuf.java:1408) ~[netty-all-4.1.9.Final.jar:4.1.9.Final] at io.netty.buffer.AbstractByteBuf.checkReadableBytes0(AbstractByteBuf.java:1394) ~[netty-all-4.1.9.Final.jar:4.1.9.Final] at io.netty.buffer.AbstractByteBuf.readInt(AbstractByteBuf.java:766) ~[netty-all-4.1.9.Final.jar:4.1.9.Final] at ZombieAwareness.EntityScent.readSpawnData(EntityScent.java:172) ~[EntityScent.class:?] at net.minecraftforge.fml.common.network.internal.EntitySpawnHandler.spawnEntity(EntitySpawnHandler.java:128) ~[EntitySpawnHandler.class:?] at net.minecraftforge.fml.common.network.internal.EntitySpawnHandler.process(EntitySpawnHandler.java:63) ~[EntitySpawnHandler.class:?] at net.minecraftforge.fml.common.network.internal.EntitySpawnHandler.lambda$channelRead0$0(EntitySpawnHandler.java:55) ~[EntitySpawnHandler.class:?] at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_151] at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_151] at net.minecraft.util.Util.func_181617_a(SourceFile:46) ~[h.class:?] ... 9 more

Seems its an issue in forge itself that is now fixed, update to at least 2543 MinecraftForge/MinecraftForge#4523