Program: 51601
Project: 51601
Buggy source:
@Override public void simpleMode(InventoryClickEvent event){
  DecimalFormat f=new DecimalFormat("String_Node_Str");
  int slot=event.getSlot();
  if (slot < 0) {
    event.setCursor(null);
    return;
  }
  boolean top=event.getView().convertSlot(event.getRawSlot()) == event.getRawSlot();
  if (top) {
    if (event.isShiftClick()) {
      ((Player)event.getWhoClicked()).sendMessage(ChatColor.GOLD + "String_Node_Str");
      event.setCancelled(true);
      return;
    }
    if (isManagementSlot(slot,1)) {
      if (isWool(event.getCurrentItem(),itemsConfig.getItemManagement(7))) {
        switchInventory(TraderStatus.SELL);
      }
 else       if (isWool(event.getCurrentItem(),itemsConfig.getItemManagement(0))) {
        if (!permissionsManager.has(player,"String_Node_Str")) {
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str"));
        }
 else {
          switchInventory(TraderStatus.SELL);
        }
      }
 else       if (isWool(event.getCurrentItem(),itemsConfig.getItemManagement(1))) {
        if (!permissionsManager.has(player,"String_Node_Str")) {
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str"));
        }
 else {
          switchInventory(TraderStatus.BUY);
        }
      }
    }
 else     if (equalsTraderStatus(TraderStatus.SELL)) {
      if (selectItem(slot,TraderStatus.SELL).hasSelectedItem()) {
        if (getSelectedItem().hasMultipleAmouts() && permissionsManager.has(player,"String_Node_Str")) {
          switchInventory(getSelectedItem());
          setTraderStatus(TraderStatus.SELL_AMOUNT);
        }
 else {
          double price=getPrice(player,"String_Node_Str");
          if (!checkLimits()) {
            Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_LIMIT));
            player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
          }
 else           if (!inventoryHasPlace(0)) {
            player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
            Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_SPACE));
          }
 else           if (!buyTransaction(price)) {
            player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
            Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_MONEY));
          }
 else {
            player.sendMessage(locale.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str" + getSelectedItem().getAmount()).replace("String_Node_Str",f.format(price)));
            addSelectedToInventory(0);
            updateLimits();
            Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.SUCCESS_SELL));
            log("String_Node_Str",getSelectedItem().getItemStack().getTypeId(),getSelectedItem().getItemStack().getData().getData(),getSelectedItem().getAmount(),price);
          }
        }
      }
    }
 else     if (equalsTraderStatus(TraderStatus.SELL_AMOUNT)) {
      if (!event.getCurrentItem().getType().equals(Material.AIR)) {
        double price=getPrice(player,"String_Node_Str",slot);
        if (!checkLimits(slot)) {
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_LIMIT));
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
        }
 else         if (!inventoryHasPlace(slot)) {
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_SPACE));
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
        }
 else         if (!buyTransaction(price)) {
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_MONEY));
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
        }
 else {
          player.sendMessage(locale.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str" + getSelectedItem().getAmount(slot)).replace("String_Node_Str",f.format(price)));
          addSelectedToInventory(slot);
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),event.getWhoClicked(),this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.SUCCESS_SELL));
          updateLimits(slot);
          switchInventory(getSelectedItem());
          log("String_Node_Str",getSelectedItem().getItemStack().getTypeId(),getSelectedItem().getItemStack().getData().getData(),getSelectedItem().getAmount(slot),price);
        }
      }
    }
  }
 else {
    if (equalsTraderStatus(TraderStatus.BUY)) {
      if (selectItem(event.getCurrentItem(),TraderStatus.BUY,true,true).hasSelectedItem()) {
        double price=getPrice(player,"String_Node_Str");
        int scale=event.getCurrentItem().getAmount() / getSelectedItem().getAmount();
        if (!checkBuyLimits(scale)) {
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_LIMIT));
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
        }
 else         if (!sellTransaction(price * scale,event.getCurrentItem())) {
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_MONEY));
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
        }
 else {
          player.sendMessage(locale.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str" + getSelectedItem().getAmount() * scale).replace("String_Node_Str",f.format(price * scale)));
          updateBuyLimits(scale);
          NBTTagEditor.removeDescription(event.getCurrentItem());
          removeFromInventory(event.getCurrentItem(),event);
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),event.getWhoClicked(),this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.SUCCESS_BUY));
          log("String_Node_Str",getSelectedItem().getItemStack().getTypeId(),getSelectedItem().getItemStack().getData().getData(),getSelectedItem().getAmount() * scale,price * scale);
        }
      }
    }
 else     if (equalsTraderStatus(TraderStatus.SELL_AMOUNT)) {
      event.setCancelled(true);
      return;
    }
 else     if (selectItem(event.getCurrentItem(),TraderStatus.BUY,true,true).hasSelectedItem()) {
      double price=getPrice(player,"String_Node_Str");
      int scale=event.getCurrentItem().getAmount() / getSelectedItem().getAmount();
      if (!permissionsManager.has(player,"String_Node_Str")) {
        player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
      }
 else       if (!checkBuyLimits(scale)) {
        Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),event.getWhoClicked(),this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_MONEY));
        player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
      }
 else       if (!sellTransaction(price * scale,event.getCurrentItem())) {
        Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),event.getWhoClicked(),this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_MONEY));
        player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
      }
 else {
        player.sendMessage(locale.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str" + getSelectedItem().getAmount() * scale).replace("String_Node_Str",f.format(price * scale)));
        updateBuyLimits(scale);
        Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),event.getWhoClicked(),this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.SUCCESS_BUY));
        NBTTagEditor.removeDescription(event.getCurrentItem());
        removeFromInventory(event.getCurrentItem(),event);
        log("String_Node_Str",getSelectedItem().getItemStack().getTypeId(),getSelectedItem().getItemStack().getData().getData(),getSelectedItem().getAmount() * scale,price * scale);
      }
    }
  }
  event.setCancelled(true);
}

Fixed version (ground truth):
@Override public void simpleMode(InventoryClickEvent event){
  DecimalFormat f=new DecimalFormat("String_Node_Str");
  int slot=event.getSlot();
  if (slot < 0) {
    event.setCursor(null);
    return;
  }
  boolean top=event.getView().convertSlot(event.getRawSlot()) == event.getRawSlot();
  if (top) {
    if (event.isShiftClick()) {
      ((Player)event.getWhoClicked()).sendMessage(ChatColor.GOLD + "String_Node_Str");
      event.setCancelled(true);
      return;
    }
    if (isManagementSlot(slot,1)) {
      if (isWool(event.getCurrentItem(),itemsConfig.getItemManagement(7))) {
        switchInventory(TraderStatus.SELL);
      }
 else       if (isWool(event.getCurrentItem(),itemsConfig.getItemManagement(0))) {
        if (!permissionsManager.has(player,"String_Node_Str")) {
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str"));
        }
 else {
          switchInventory(TraderStatus.SELL);
        }
      }
 else       if (isWool(event.getCurrentItem(),itemsConfig.getItemManagement(1))) {
        if (!permissionsManager.has(player,"String_Node_Str")) {
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str"));
        }
 else {
          switchInventory(TraderStatus.BUY);
        }
      }
    }
 else     if (equalsTraderStatus(TraderStatus.SELL)) {
      if (selectItem(slot,TraderStatus.SELL).hasSelectedItem()) {
        if (getSelectedItem().hasMultipleAmouts() && permissionsManager.has(player,"String_Node_Str")) {
          switchInventory(getSelectedItem());
          setTraderStatus(TraderStatus.SELL_AMOUNT);
        }
 else {
          double price=getPrice(player,"String_Node_Str");
          if (!checkLimits()) {
            Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_LIMIT));
            player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
          }
 else           if (!inventoryHasPlace(0)) {
            player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
            Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_SPACE));
          }
 else           if (!buyTransaction(price)) {
            player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
            Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_MONEY));
          }
 else {
            player.sendMessage(locale.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str" + getSelectedItem().getAmount()).replace("String_Node_Str",f.format(price)));
            addSelectedToInventory(0);
            updateLimits();
            Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.SUCCESS_SELL));
            log("String_Node_Str",getSelectedItem().getItemStack().getTypeId(),getSelectedItem().getItemStack().getData().getData(),getSelectedItem().getAmount(),price);
          }
        }
      }
    }
 else     if (equalsTraderStatus(TraderStatus.SELL_AMOUNT)) {
      if (!event.getCurrentItem().getType().equals(Material.AIR)) {
        double price=getPrice(player,"String_Node_Str",slot);
        if (!checkLimits(slot)) {
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_LIMIT));
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
        }
 else         if (!inventoryHasPlace(slot)) {
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_SPACE));
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
        }
 else         if (!buyTransaction(price)) {
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_MONEY));
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
        }
 else {
          player.sendMessage(locale.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str" + getSelectedItem().getAmount(slot)).replace("String_Node_Str",f.format(price)));
          addSelectedToInventory(slot);
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),event.getWhoClicked(),this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.SUCCESS_SELL));
          updateLimits(slot);
          switchInventory(getSelectedItem());
          log("String_Node_Str",getSelectedItem().getItemStack().getTypeId(),getSelectedItem().getItemStack().getData().getData(),getSelectedItem().getAmount(slot),price);
        }
      }
    }
  }
 else {
    if (equalsTraderStatus(TraderStatus.BUY)) {
      if (selectItem(event.getCurrentItem(),TraderStatus.BUY,true).hasSelectedItem()) {
        double price=getPrice(player,"String_Node_Str");
        int scale=event.getCurrentItem().getAmount() / getSelectedItem().getAmount();
        if (!checkBuyLimits(scale)) {
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_LIMIT));
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
        }
 else         if (!sellTransaction(price * scale,event.getCurrentItem())) {
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),player,this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_MONEY));
          player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
        }
 else {
          player.sendMessage(locale.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str" + getSelectedItem().getAmount() * scale).replace("String_Node_Str",f.format(price * scale)));
          updateBuyLimits(scale);
          NBTTagEditor.removeDescription(event.getCurrentItem());
          removeFromInventory(event.getCurrentItem(),event);
          Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),event.getWhoClicked(),this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.SUCCESS_BUY));
          log("String_Node_Str",getSelectedItem().getItemStack().getTypeId(),getSelectedItem().getItemStack().getData().getData(),getSelectedItem().getAmount() * scale,price * scale);
        }
      }
    }
 else     if (equalsTraderStatus(TraderStatus.SELL_AMOUNT)) {
      event.setCancelled(true);
      return;
    }
 else     if (selectItem(event.getCurrentItem(),TraderStatus.BUY,true).hasSelectedItem()) {
      double price=getPrice(player,"String_Node_Str");
      int scale=event.getCurrentItem().getAmount() / getSelectedItem().getAmount();
      if (!permissionsManager.has(player,"String_Node_Str")) {
        player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
      }
 else       if (!checkBuyLimits(scale)) {
        Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),event.getWhoClicked(),this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_MONEY));
        player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
      }
 else       if (!sellTransaction(price * scale,event.getCurrentItem())) {
        Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),event.getWhoClicked(),this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.FAIL_MONEY));
        player.sendMessage(localeManager.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str"));
      }
 else {
        player.sendMessage(locale.getLocaleString("String_Node_Str","String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str" + getSelectedItem().getAmount() * scale).replace("String_Node_Str",f.format(price * scale)));
        updateBuyLimits(scale);
        Bukkit.getServer().getPluginManager().callEvent(new TraderTransactionEvent(this,this.getNpc(),event.getWhoClicked(),this.getTraderStatus(),this.getSelectedItem(),price,TransactionResult.SUCCESS_BUY));
        NBTTagEditor.removeDescription(event.getCurrentItem());
        removeFromInventory(event.getCurrentItem(),event);
        log("String_Node_Str",getSelectedItem().getItemStack().getTypeId(),getSelectedItem().getItemStack().getData().getData(),getSelectedItem().getAmount() * scale,price * scale);
      }
    }
  }
  event.setCancelled(true);
}