Program: 81851
Project: 81851
Buggy source:
@SubscribeEvent public void onPacketFromClient(FMLNetworkEvent.ServerCustomPacketEvent event){
  final EntityPlayerMP entP=((NetHandlerPlayServer)event.getHandler()).playerEntity;
  try {
    final NBTTagCompound nbt=PacketHelper.readNBTTagCompound(event.getPacket().payload());
    final String packetCommand=nbt.getString("String_Node_Str");
    final String command=nbt.getString("String_Node_Str");
    Weather.dbg("String_Node_Str" + packetCommand + "String_Node_Str"+ command);
    entP.mcServer.addScheduledTask(new Runnable(){
      @Override public void run(){
        if (packetCommand.equals("String_Node_Str")) {
          if (command.equals("String_Node_Str")) {
            ServerTickHandler.playerClientRequestsFullSync(entP);
          }
        }
 else         if (packetCommand.equals("String_Node_Str")) {
          Weather.dbg("String_Node_Str" + command);
          if (command.equals("String_Node_Str")) {
            Weather.dbg("String_Node_Str");
            NBTTagCompound sendNBT=new NBTTagCompound();
            sendNBT.setString("String_Node_Str","String_Node_Str");
            sendNBT.setString("String_Node_Str","String_Node_Str");
            sendNBT.setBoolean("String_Node_Str",true);
            sendNBT.setBoolean("String_Node_Str",FMLCommonHandler.instance().getMinecraftServerInstance().isSinglePlayer() || FMLCommonHandler.instance().getMinecraftServerInstance().getPlayerList().canSendCommands(entP.getGameProfile()));
            sendNBT.setTag("String_Node_Str",WeatherUtilConfig.nbtServerData);
            sendNBT.setTag("String_Node_Str",WeatherUtilConfig.createNBTDimensionListing());
            Weather.eventChannel.sendTo(PacketHelper.getNBTPacket(sendNBT,Weather.eventChannelName),entP);
          }
 else           if (command.equals("String_Node_Str")) {
            if (FMLCommonHandler.instance().getMinecraftServerInstance().isSinglePlayer() || FMLCommonHandler.instance().getMinecraftServerInstance().getPlayerList().canSendCommands(entP.getGameProfile())) {
              WeatherUtilConfig.nbtReceiveClientData(nbt.getCompoundTag("String_Node_Str"));
            }
          }
        }
      }
    }
);
  }
 catch (  Exception ex) {
    ex.printStackTrace();
  }
}

Fixed version (ground truth):
@SubscribeEvent public void onPacketFromClient(FMLNetworkEvent.ServerCustomPacketEvent event){
  final EntityPlayerMP entP=((NetHandlerPlayServer)event.getHandler()).player;
  try {
    final NBTTagCompound nbt=PacketHelper.readNBTTagCompound(event.getPacket().payload());
    final String packetCommand=nbt.getString("String_Node_Str");
    final String command=nbt.getString("String_Node_Str");
    Weather.dbg("String_Node_Str" + packetCommand + "String_Node_Str"+ command);
    entP.mcServer.addScheduledTask(new Runnable(){
      @Override public void run(){
        if (packetCommand.equals("String_Node_Str")) {
          if (command.equals("String_Node_Str")) {
            ServerTickHandler.playerClientRequestsFullSync(entP);
          }
        }
 else         if (packetCommand.equals("String_Node_Str")) {
          Weather.dbg("String_Node_Str" + command);
          if (command.equals("String_Node_Str")) {
            Weather.dbg("String_Node_Str");
            NBTTagCompound sendNBT=new NBTTagCompound();
            sendNBT.setString("String_Node_Str","String_Node_Str");
            sendNBT.setString("String_Node_Str","String_Node_Str");
            sendNBT.setBoolean("String_Node_Str",true);
            sendNBT.setBoolean("String_Node_Str",FMLCommonHandler.instance().getMinecraftServerInstance().isSinglePlayer() || FMLCommonHandler.instance().getMinecraftServerInstance().getPlayerList().canSendCommands(entP.getGameProfile()));
            sendNBT.setTag("String_Node_Str",WeatherUtilConfig.nbtServerData);
            sendNBT.setTag("String_Node_Str",WeatherUtilConfig.createNBTDimensionListing());
            Weather.eventChannel.sendTo(PacketHelper.getNBTPacket(sendNBT,Weather.eventChannelName),entP);
          }
 else           if (command.equals("String_Node_Str")) {
            if (FMLCommonHandler.instance().getMinecraftServerInstance().isSinglePlayer() || FMLCommonHandler.instance().getMinecraftServerInstance().getPlayerList().canSendCommands(entP.getGameProfile())) {
              WeatherUtilConfig.nbtReceiveClientData(nbt.getCompoundTag("String_Node_Str"));
            }
          }
        }
      }
    }
);
  }
 catch (  Exception ex) {
    ex.printStackTrace();
  }
}