Program: 2033
Project: 2033
Buggy source:
@Override public boolean onCommand(CommandSender sender,Command command,String commandLabel,String[] args){
  if (!(sender instanceof Player)) {
    sender.sendMessage(MessageUtils.mustBeIngameMessage);
    return true;
  }
  Player player=(Player)sender;
  HumanNPC npc=null;
  boolean returnval=false;
  if (NPCManager.validateSelected((Player)sender))   npc=NPCManager.getNPC(NPCManager.NPCSelected.get(player.getName()));
 else {
    player.sendMessage(ChatColor.RED + MessageUtils.mustHaveNPCSelectedMessage);
    return true;
  }
  if (!NPCManager.validateOwnership(player,npc.getUID())) {
    player.sendMessage(MessageUtils.notOwnerMessage);
    return true;
  }
  if (args.length == 0) {
    sender.sendMessage(ChatColor.RED + "String_Node_Str");
    return true;
  }
 else {
    if (args[0].equals("String_Node_Str")) {
      if (BasicExecutor.hasPermission("String_Node_Str",sender)) {
        if (!TraderPropertyPool.isTrader(npc.getUID())) {
          buyTrader(npc,player);
        }
 else {
          toggleTrader(npc,player);
        }
      }
 else {
        sender.sendMessage(MessageUtils.noPermissionsMessage);
      }
      returnval=true;
    }
 else     if (args[0].equals("String_Node_Str")) {
      sender.sendMessage("String_Node_Str");
    }
 else     if (args[0].equals("String_Node_Str")) {
      if (BasicExecutor.hasPermission("String_Node_Str",sender)) {
        if (!HealerPropertyPool.isHealer(npc.getUID())) {
          buyHealer(npc,player);
        }
 else {
          toggleHealer(npc,player);
        }
        returnval=true;
      }
 else {
        sender.sendMessage(MessageUtils.noPermissionsMessage);
      }
    }
 else     if (args[0].equals("String_Node_Str")) {
      sender.sendMessage("String_Node_Str");
    }
 else     if (args[0].equals("String_Node_Str")) {
      sender.sendMessage("String_Node_Str");
    }
 else     if (args[0].equals("String_Node_Str")) {
      if (args[1].equals("String_Node_Str")) {
        toggleAllOn(npc,player);
      }
 else       if (args[1].equals("String_Node_Str")) {
        toggleAllOff(npc,player);
      }
      returnval=true;
    }
 else {
      player.sendMessage(ChatColor.RED + "String_Node_Str");
      return true;
    }
    TraderPropertyPool.saveTraderState(npc);
  }
  return returnval;
}

Fixed version (ground truth):
@Override public boolean onCommand(CommandSender sender,Command command,String commandLabel,String[] args){
  if (!(sender instanceof Player)) {
    sender.sendMessage(MessageUtils.mustBeIngameMessage);
    return true;
  }
  Player player=(Player)sender;
  HumanNPC npc=null;
  boolean returnval=false;
  if (NPCManager.validateSelected((Player)sender))   npc=NPCManager.getNPC(NPCManager.NPCSelected.get(player.getName()));
 else {
    player.sendMessage(ChatColor.RED + MessageUtils.mustHaveNPCSelectedMessage);
    return true;
  }
  if (!NPCManager.validateOwnership(player,npc.getUID())) {
    player.sendMessage(MessageUtils.notOwnerMessage);
    return true;
  }
  if (args.length == 0) {
    sender.sendMessage(ChatColor.RED + "String_Node_Str");
    return true;
  }
 else {
    if (args[0].equals("String_Node_Str")) {
      if (BasicExecutor.hasPermission("String_Node_Str",sender)) {
        if (!TraderPropertyPool.isTrader(npc.getUID())) {
          buyState(player,npc.getTraderNPC(),Operation.TRADER_NPC_CREATE);
        }
 else {
          toggleState(player,npc.getTraderNPC());
        }
      }
 else {
        sender.sendMessage(MessageUtils.noPermissionsMessage);
      }
      returnval=true;
    }
 else     if (args[0].equals("String_Node_Str")) {
      sender.sendMessage("String_Node_Str");
    }
 else     if (args[0].equals("String_Node_Str")) {
      if (BasicExecutor.hasPermission("String_Node_Str",sender)) {
        if (!HealerPropertyPool.isHealer(npc.getUID())) {
          buyState(player,npc.getHealerNPC(),Operation.HEALER_NPC_CREATE);
        }
 else {
          toggleState(player,npc.getHealerNPC());
        }
        returnval=true;
      }
 else {
        sender.sendMessage(MessageUtils.noPermissionsMessage);
      }
    }
 else     if (args[0].equals("String_Node_Str")) {
      sender.sendMessage("String_Node_Str");
      returnval=true;
    }
 else     if (args[0].equals("String_Node_Str")) {
      sender.sendMessage("String_Node_Str");
      returnval=true;
    }
 else     if (args.length == 2 && args[0].equals("String_Node_Str")) {
      if (args[1].equals("String_Node_Str"))       toggleAll(npc,player,true);
 else       if (args[1].equals("String_Node_Str"))       toggleAll(npc,player,false);
      returnval=true;
    }
 else {
      player.sendMessage(ChatColor.RED + "String_Node_Str");
      return true;
    }
  }
  return returnval;
}