This is happening a few times lately both with the 1.11 and 1.12 versions. The game freezes and stops responding. This is the log where I see a NetworkDispatcher exception and a NullPointer exception:
12:41:44 game info [10:41:44] [replaymod-async-sender/ERROR] [FML]: NetworkDispatcher exception
12:41:44 game info java.lang.NullPointerException: null
12:41:44 game info at io.netty.channel.ChannelOutboundBuffer.addFlush(ChannelOutboundBuffer.java:146) ~[ChannelOutboundBuffer.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannel$AbstractUnsafe.flush(AbstractChannel.java:822) ~[AbstractChannel$AbstractUnsafe.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.DefaultChannelPipeline$HeadContext.flush(DefaultChannelPipeline.java:1296) ~[DefaultChannelPipeline$HeadContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.flush(NetworkDispatcher.java:547) [NetworkDispatcher.class:?]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:802) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:814) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:794) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:831) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:1032) [DefaultChannelPipeline.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:296) [AbstractChannel.class:4.1.9.Final]
12:41:44 game info at net.minecraft.network.NetworkManager.func_150732_b(NetworkManager.java:225) [gw.class:?]
12:41:44 game info at net.minecraft.network.NetworkManager.func_179290_a(NetworkManager.java:168) [gw.class:?]
12:41:44 game info at net.minecraft.client.network.NetHandlerPlayClient.func_147297_a(NetHandlerPlayClient.java:803) [brx.class:?]
12:41:44 game info at net.minecraft.client.network.NetHandlerPlayClient.func_147272_a(NetHandlerPlayClient.java:1642) [brx.class:?]
12:41:44 game info at net.minecraft.network.play.server.SPacketKeepAlive.func_148833_a(SourceFile:21) [jd.class:?]
12:41:44 game info at net.minecraft.network.play.server.SPacketKeepAlive.func_148833_a(SourceFile:8) [jd.class:?]
12:41:44 game info at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:147) [gw.class:?]
12:41:44 game info at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:49) [gw.class:?]
12:41:44 game info at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [SimpleChannelInboundHandler.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:280) [NetworkDispatcher.class:?]
12:41:44 game info at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:75) [NetworkDispatcher.class:?]
12:41:44 game info at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [SimpleChannelInboundHandler.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) [AbstractChannelHandlerContext.class:4.1.9.Final]
12:41:44 game info at io.netty.channel.ChannelInboundHandlerAdapter.channelRead(ChannelInboundHandlerAdapter.java:86) [ChannelInboundHandlerAdapter.class:4.1.9.Final]
12:41:44 game info at com.replaymod.replay.ReplaySender.channelRead(ReplaySender.java:290) [ReplaySender.class:?]
12:41:44 game info at com.replaymod.replay.ReplaySender$3.run(ReplaySender.java:620) [ReplaySender$3.class:?]
12:41:44 game info at java.lang.Thread.run(Thread.java:745) [?:1.8.0_25]
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: java.lang.NullPointerException
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.ChannelOutboundBuffer.addFlush(ChannelOutboundBuffer.java:146)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannel$AbstractUnsafe.flush(AbstractChannel.java:822)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.DefaultChannelPipeline$HeadContext.flush(DefaultChannelPipeline.java:1296)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.flush(NetworkDispatcher.java:547)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:802)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:814)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:794)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:831)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:1032)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:296)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraft.network.NetworkManager.func_150732_b(NetworkManager.java:225)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraft.network.NetworkManager.func_179290_a(NetworkManager.java:168)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraft.client.network.NetHandlerPlayClient.func_147297_a(NetHandlerPlayClient.java:803)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraft.client.network.NetHandlerPlayClient.func_147272_a(NetHandlerPlayClient.java:1642)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraft.network.play.server.SPacketKeepAlive.func_148833_a(SourceFile:21)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraft.network.play.server.SPacketKeepAlive.func_148833_a(SourceFile:8)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:147)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraft.network.NetworkManager.channelRead0(NetworkManager.java:49)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:280)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.channelRead0(NetworkDispatcher.java:75)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at io.netty.channel.ChannelInboundHandlerAdapter.channelRead(ChannelInboundHandlerAdapter.java:86)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at com.replaymod.replay.ReplaySender.channelRead(ReplaySender.java:290)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at com.replaymod.replay.ReplaySender$3.run(ReplaySender.java:620)
12:41:44 game info [10:41:44] [replaymod-async-sender/INFO]: [STDERR]: at java.lang.Thread.run(Thread.java:745)
