Program: 42063
Project: 42063
Buggy source:
public boolean exec(IPlayer player,String[] args){
  IWorld world=player.getWorld();
  if (manager.isPlotWorld(world)) {
    PlotMapInfo pmi=manager.getMap(world);
    if (manager.isEconomyEnabled(pmi)) {
      if (pmi.isCanPutOnSale()) {
        if (player.hasPermission(PermissionNames.USER_SELL) || player.hasPermission(PermissionNames.ADMIN_SELL)) {
          String id=manager.getPlotId(player);
          if (id.isEmpty()) {
            player.sendMessage("String_Node_Str" + C("String_Node_Str"));
          }
 else           if (!manager.isPlotAvailable(id,pmi)) {
            Plot plot=manager.getPlotById(id,pmi);
            if (plot.getOwnerId().equals(player.getUniqueId()) || player.hasPermission(PermissionNames.ADMIN_SELL)) {
              InternalPlotSellChangeEvent event;
              if (plot.isForSale()) {
                event=serverBridge.getEventFactory().callPlotSellChangeEvent(plugin,world,plot,player,plot.getCustomPrice(),false);
                if (!event.isCancelled()) {
                  plot.setCustomPrice(0.0);
                  plot.setForSale(false);
                  plot.updateField("String_Node_Str",0);
                  plot.updateField("String_Node_Str",false);
                  manager.adjustWall(player);
                  manager.removeSellSign(world,id);
                  player.sendMessage(C("String_Node_Str"));
                  if (isAdvancedLogging()) {
                    serverBridge.getLogger().info(player.getName() + "String_Node_Str" + C("String_Node_Str")+ "String_Node_Str"+ id+ "String_Node_Str"+ C("String_Node_Str"));
                  }
                }
              }
 else {
                double price=pmi.getSellToPlayerPrice();
                if (args.length == 2) {
                  try {
                    price=Double.parseDouble(args[1]);
                  }
 catch (                  Exception e) {
                    player.sendMessage(C("String_Node_Str") + "String_Node_Str" + C("String_Node_Str")+ "String_Node_Str"+ C("String_Node_Str")+ "String_Node_Str");
                    return true;
                  }
                }
                if (price < 0.0) {
                  player.sendMessage("String_Node_Str" + C("String_Node_Str"));
                }
 else {
                  event=serverBridge.getEventFactory().callPlotSellChangeEvent(plugin,world,plot,player,price,true);
                  if (!event.isCancelled()) {
                    plot.setCustomPrice(price);
                    plot.setForSale(true);
                    plot.updateField("String_Node_Str",price);
                    plot.updateField("String_Node_Str",true);
                    manager.adjustWall(player);
                    manager.setSellSign(world,plot);
                    player.sendMessage(C("String_Node_Str"));
                    if (isAdvancedLogging()) {
                      serverBridge.getLogger().info(player.getName() + "String_Node_Str" + C("String_Node_Str")+ "String_Node_Str"+ id+ "String_Node_Str"+ C("String_Node_Str")+ "String_Node_Str"+ price);
                    }
                  }
                }
              }
            }
 else {
              player.sendMessage("String_Node_Str" + C("String_Node_Str"));
            }
          }
 else {
            player.sendMessage("String_Node_Str" + C("String_Node_Str") + "String_Node_Str"+ id+ "String_Node_Str"+ C("String_Node_Str"));
          }
        }
 else {
          player.sendMessage("String_Node_Str" + C("String_Node_Str"));
          return false;
        }
      }
 else {
        player.sendMessage("String_Node_Str" + C("String_Node_Str"));
      }
    }
 else {
      player.sendMessage("String_Node_Str" + C("String_Node_Str"));
    }
  }
  return true;
}

Fixed version (ground truth):
public boolean exec(IPlayer player,String[] args){
  IWorld world=player.getWorld();
  if (manager.isPlotWorld(world)) {
    PlotMapInfo pmi=manager.getMap(world);
    if (manager.isEconomyEnabled(pmi)) {
      if (pmi.isCanPutOnSale()) {
        if (player.hasPermission(PermissionNames.USER_SELL) || player.hasPermission(PermissionNames.ADMIN_SELL)) {
          String id=manager.getPlotId(player);
          if (id.isEmpty()) {
            player.sendMessage("String_Node_Str" + C("String_Node_Str"));
          }
 else           if (!manager.isPlotAvailable(id,pmi)) {
            Plot plot=manager.getPlotById(id,pmi);
            if (plot.isAuctioned()) {
              player.sendMessage(C("String_Node_Str"));
              return true;
            }
            if (plot.getOwnerId().equals(player.getUniqueId()) || player.hasPermission(PermissionNames.ADMIN_SELL)) {
              InternalPlotSellChangeEvent event;
              if (plot.isForSale()) {
                event=serverBridge.getEventFactory().callPlotSellChangeEvent(plugin,world,plot,player,plot.getCustomPrice(),false);
                if (!event.isCancelled()) {
                  plot.setCustomPrice(0.0);
                  plot.setForSale(false);
                  plot.updateField("String_Node_Str",0);
                  plot.updateField("String_Node_Str",false);
                  manager.adjustWall(player);
                  manager.removeSellSign(world,id);
                  player.sendMessage(C("String_Node_Str"));
                  if (isAdvancedLogging()) {
                    serverBridge.getLogger().info(player.getName() + "String_Node_Str" + C("String_Node_Str")+ "String_Node_Str"+ id+ "String_Node_Str"+ C("String_Node_Str"));
                  }
                }
              }
 else {
                double price=pmi.getSellToPlayerPrice();
                if (args.length == 2) {
                  try {
                    price=Double.parseDouble(args[1]);
                  }
 catch (                  Exception e) {
                    player.sendMessage(C("String_Node_Str") + "String_Node_Str" + C("String_Node_Str")+ "String_Node_Str"+ C("String_Node_Str")+ "String_Node_Str");
                    return true;
                  }
                }
                if (price < 0.0) {
                  player.sendMessage("String_Node_Str" + C("String_Node_Str"));
                }
 else {
                  event=serverBridge.getEventFactory().callPlotSellChangeEvent(plugin,world,plot,player,price,true);
                  if (!event.isCancelled()) {
                    plot.setCustomPrice(price);
                    plot.setForSale(true);
                    plot.updateField("String_Node_Str",price);
                    plot.updateField("String_Node_Str",true);
                    manager.adjustWall(player);
                    manager.setSellSign(world,plot);
                    player.sendMessage(C("String_Node_Str"));
                    if (isAdvancedLogging()) {
                      serverBridge.getLogger().info(player.getName() + "String_Node_Str" + C("String_Node_Str")+ "String_Node_Str"+ id+ "String_Node_Str"+ C("String_Node_Str")+ "String_Node_Str"+ price);
                    }
                  }
                }
              }
            }
 else {
              player.sendMessage("String_Node_Str" + C("String_Node_Str"));
            }
          }
 else {
            player.sendMessage("String_Node_Str" + C("String_Node_Str") + "String_Node_Str"+ id+ "String_Node_Str"+ C("String_Node_Str"));
          }
        }
 else {
          player.sendMessage("String_Node_Str" + C("String_Node_Str"));
          return false;
        }
      }
 else {
        player.sendMessage("String_Node_Str" + C("String_Node_Str"));
      }
    }
 else {
      player.sendMessage("String_Node_Str" + C("String_Node_Str"));
    }
  }
  return true;
}