Netty Deadlock Crash

Not sure what caused this:

Forge: 11.15.1.1902
SpongeForge: 1.8.9-1890-4.2.0-BETA-1693

01.10 22:23:26 [Server] Netty Epoll Server IO #6/WARN [io.netty.util.concurrent.DefaultPromise]: An exception was thrown by net.minecraft.network.NetHandlerPlayServer$1.operationComplete()
01.10 22:23:26 [Server] INFO io.netty.util.concurrent.BlockingOperationException: [email protected](uncancellable)
01.10 22:23:26 [Server] INFO at io.netty.util.concurrent.DefaultPromise.checkDeadLock(DefaultPromise.java:390) ~[DefaultPromise.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.DefaultChannelPromise.checkDeadLock(DefaultChannelPromise.java:157) ~[DefaultChannelPromise.class:?]
01.10 22:23:26 [Server] INFO at io.netty.util.concurrent.DefaultPromise.awaitUninterruptibly(DefaultPromise.java:283) ~[DefaultPromise.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.DefaultChannelPromise.awaitUninterruptibly(DefaultChannelPromise.java:135) ~[DefaultChannelPromise.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.DefaultChannelPromise.awaitUninterruptibly(DefaultChannelPromise.java:28) ~[DefaultChannelPromise.class:?]
01.10 22:23:26 [Server] INFO at net.minecraft.network.NetworkManager.func_150718_a(NetworkManager.java:304) ~[ek.class:?]
01.10 22:23:26 [Server] INFO at net.minecraft.network.NetHandlerPlayServer$1.operationComplete(NetHandlerPlayServer.java:172) ~[lm$1.class:?]
01.10 22:23:26 [Server] INFO at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:680) [DefaultPromise.class:?]
01.10 22:23:26 [Server] INFO at io.netty.util.concurrent.DefaultPromise.notifyListeners0(DefaultPromise.java:603) [DefaultPromise.class:?]
01.10 22:23:26 [Server] INFO at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:563) [DefaultPromise.class:?]
01.10 22:23:26 [Server] INFO at io.netty.util.concurrent.DefaultPromise.trySuccess(DefaultPromise.java:406) [DefaultPromise.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.DefaultChannelPromise.trySuccess(DefaultChannelPromise.java:82) [DefaultChannelPromise.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.ChannelOutboundBuffer.safeSuccess(ChannelOutboundBuffer.java:523) [ChannelOutboundBuffer.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.ChannelOutboundBuffer.remove(ChannelOutboundBuffer.java:247) [ChannelOutboundBuffer.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.ChannelOutboundBuffer.removeBytes(ChannelOutboundBuffer.java:322) [ChannelOutboundBuffer.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.epoll.EpollSocketChannel.writeBytesMultiple(EpollSocketChannel.java:212) [EpollSocketChannel.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.epoll.EpollSocketChannel.doWriteMultiple(EpollSocketChannel.java:364) [EpollSocketChannel.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.epoll.EpollSocketChannel.doWrite(EpollSocketChannel.java:317) [EpollSocketChannel.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.AbstractChannel$AbstractUnsafe.flush0(AbstractChannel.java:707) [AbstractChannel$AbstractUnsafe.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.epoll.AbstractEpollChannel$AbstractEpollUnsafe.epollOutReady(AbstractEpollChannel.java:248) [AbstractEpollChannel$AbstractEpollUnsafe.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.epoll.EpollSocketChannel$EpollSocketUnsafe.epollOutReady(EpollSocketChannel.java:623) [EpollSocketChannel$EpollSocketUnsafe.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:322) [EpollEventLoop.class:?]
01.10 22:23:26 [Server] INFO at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:264) [EpollEventLoop.class:?]
01.10 22:23:26 [Server] INFO at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) [SingleThreadEventExecutor$2.class:?]
01.10 22:23:26 [Server] INFO at java.lang.Thread.run(Thread.java:745) [?:1.8.0_92]
01.10 22:24:02 [Multicraft] Terminating server via signal
01.10 22:24:03 [Multicraft] Server shut down (terminating)
01.10 22:24:03 [Multicraft] Looks like a crash, check the server console. Return value: 143

---- Minecraft Crash Report ----

WARNING: coremods are present:
  SpongeCoremod (spongeforge-1.8.9-1890-4.2.0-BETA-1693.jar)
  Java8CheckerCoremod (Pixelmon-1.8.9-4.3.0-beta9-universal.jar)
Contact their authors BEFORE contacting forge

// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 10/1/16 10:44 AM
Description: Watching Server

java.lang.Error
	at net.minecraft.util.LongHashMap.func_76164_a(SourceFile:49)
	at net.minecraft.world.gen.ChunkProviderServer.getChunkIfLoaded(ChunkProviderServer.java:84)
	at net.minecraft.world.WorldServer.func_147456_g(WorldServer.java:229)
	at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:221)
	at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:690)
	at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:344)
	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:605)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:481)
	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 --
Stacktrace:
	at net.minecraft.util.LongHashMap.func_76164_a(SourceFile:49)
	at net.minecraft.world.gen.ChunkProviderServer.getChunkIfLoaded(ChunkProviderServer.java:84)
	at net.minecraft.world.WorldServer.func_147456_g(WorldServer.java:229)
	at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:221)
	at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:690)
	at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:344)
	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:605)

I have seen the first error here:
https://github.com/SpongePowered/SpongeForge/issues/927
Not sure it is related.