Program: 41997
Project: 41997
Buggy source:
public boolean execute(ICommandSender sender,String[] args) throws Exception {
  if (args.length < 2 && args.length >= 3) {
    throw new BadUsageException(getUsage());
  }
  if (args[1].length() > 16 || !validUserPattern.matcher(args[1]).matches()) {
    throw new IllegalArgumentException(C("String_Node_Str"));
  }
  IPlayer player=(IPlayer)sender;
  IWorld world=player.getWorld();
  if (player.hasPermission(PermissionNames.ADMIN_SETOWNER) && manager.isPlotWorld(world)) {
    PlotMapInfo pmi=manager.getMap(world);
    Plot plot=manager.getPlot(player);
    if (plot == null) {
      player.sendMessage("String_Node_Str");
      return true;
    }
    String newOwner=null;
    UUID newOwnerId=null;
    for (    IPlayer online : serverBridge.getOnlinePlayers()) {
      if (online.getName().equalsIgnoreCase(args[1])) {
        newOwner=online.getName();
        newOwnerId=online.getUniqueId();
        break;
      }
    }
    if (newOwnerId == null || newOwner == null) {
      player.sendMessage(C("String_Node_Str"));
      return true;
    }
    UUID oldowner=plot.getOwnerId();
    if (!oldowner.equals(newOwnerId)) {
      PlotOwnerChangeEvent event=new PlotOwnerChangeEvent(world,plot,player,newOwner);
      serverBridge.getEventBus().post(event);
      if (!event.isCancelled()) {
        plot.setForSale(false);
        manager.removeSellSign(plot,world);
        plot.resetExpire(pmi.getDaysToExpiration());
        plot.updateField("String_Node_Str",false);
        plot.setOwner(newOwner);
        plot.setOwnerId(newOwnerId);
        manager.setOwnerSign(world,plot);
        player.sendMessage(C("String_Node_Str") + "String_Node_Str" + newOwner);
      }
    }
 else {
      player.sendMessage("String_Node_Str");
    }
    return true;
  }
 else {
    return false;
  }
}

Fixed version (ground truth):
public boolean execute(ICommandSender sender,String[] args) throws Exception {
  if (args.length < 2 && args.length >= 3) {
    throw new BadUsageException(getUsage());
  }
  if (args[1].length() > 16 || !validUserPattern.matcher(args[1]).matches()) {
    throw new IllegalArgumentException(C("String_Node_Str"));
  }
  IPlayer player=(IPlayer)sender;
  IWorld world=player.getWorld();
  if (player.hasPermission(PermissionNames.ADMIN_SETOWNER) && manager.isPlotWorld(world)) {
    PlotMapInfo pmi=manager.getMap(world);
    Plot plot=manager.getPlot(player);
    if (plot == null) {
      player.sendMessage("String_Node_Str");
      return true;
    }
    String newOwner=null;
    UUID newOwnerId=null;
    for (    IPlayer online : serverBridge.getOnlinePlayers()) {
      if (online.getName().equals(args[1])) {
        newOwner=online.getName();
        newOwnerId=online.getUniqueId();
        break;
      }
    }
    if (newOwnerId == null) {
      player.sendMessage(C("String_Node_Str"));
      return true;
    }
    UUID oldowner=plot.getOwnerId();
    if (!oldowner.equals(newOwnerId)) {
      PlotOwnerChangeEvent event=new PlotOwnerChangeEvent(world,plot,player,newOwner);
      serverBridge.getEventBus().post(event);
      if (!event.isCancelled()) {
        plot.setForSale(false);
        manager.removeSellSign(plot,world);
        plot.resetExpire(pmi.getDaysToExpiration());
        plot.updateField("String_Node_Str",false);
        plot.setOwner(newOwner);
        plot.setOwnerId(newOwnerId);
        manager.setOwnerSign(world,plot);
        player.sendMessage(C("String_Node_Str") + "String_Node_Str" + newOwner);
      }
    }
 else {
      player.sendMessage("String_Node_Str");
    }
    return true;
  }
 else {
    return false;
  }
}