Program: 33933
Project: 33933
Buggy source:
@Override public void run(){
  int oldLevel=plugin.getPlayers().getIslandLevel(targetPlayer);
  plugin.getPlayers().setIslandLevel(targetPlayer,score);
  plugin.getPlayers().save(targetPlayer);
  if (plugin.getPlayers().inTeam(targetPlayer)) {
    for (    UUID member : plugin.getPlayers().getMembers(targetPlayer)) {
      plugin.getPlayers().setIslandLevel(member,score);
      plugin.getPlayers().save(member);
    }
  }
  if (sender != null) {
    if (!(sender instanceof Player)) {
      if (!report) {
        sender.sendMessage(ChatColor.GREEN + plugin.myLocale().islandislandLevelis + "String_Node_Str"+ ChatColor.WHITE+ plugin.getPlayers().getIslandLevel(targetPlayer));
      }
 else {
        for (        String line : reportLines) {
          sender.sendMessage(line);
        }
      }
    }
 else {
      if (!report) {
        if (plugin.getPlayers().getIslandLevel(targetPlayer) > oldLevel) {
          plugin.getMessages().tellOfflineTeam(targetPlayer,ChatColor.GREEN + plugin.myLocale(targetPlayer).islandislandLevelis + "String_Node_Str"+ ChatColor.WHITE+ plugin.getPlayers().getIslandLevel(targetPlayer));
        }
        if (sender instanceof Player && ((Player)sender).isOnline()) {
          String message=ChatColor.GREEN + plugin.myLocale(((Player)sender).getUniqueId()).islandislandLevelis + "String_Node_Str"+ ChatColor.WHITE+ plugin.getPlayers().getIslandLevel(targetPlayer);
          if (Settings.deathpenalty != 0) {
            message+="String_Node_Str" + plugin.myLocale(((Player)sender).getUniqueId()).levelDeaths.replace("String_Node_Str",String.valueOf(plugin.getPlayers().getDeaths(targetPlayer)));
          }
          sender.sendMessage(message);
          int requiredPoints=(Settings.levelCost * (plugin.getPlayers().getIslandLevel(targetPlayer) + 1)) - ((blocks * levelMultiplier) - (deathHandicap * Settings.deathpenalty));
          String toNextLevel=ChatColor.GREEN + plugin.myLocale(((Player)sender).getUniqueId()).islandrequiredPointsToNextLevel.replace("String_Node_Str",String.valueOf(requiredPoints));
          toNextLevel=toNextLevel.replace("String_Node_Str",String.valueOf(plugin.getPlayers().getIslandLevel(targetPlayer) + 1));
          sender.sendMessage(toNextLevel);
        }
      }
 else {
        if (((Player)sender).isOnline()) {
          for (          String line : reportLines) {
            sender.sendMessage(line);
          }
        }
      }
    }
  }
  if (plugin.getPlayers().inTeam(targetPlayer)) {
    UUID leader=plugin.getPlayers().getTeamLeader(targetPlayer);
    if (leader != null) {
      TopTen.topTenAddEntry(leader,score);
    }
  }
 else {
    TopTen.topTenAddEntry(targetPlayer,score);
  }
  Island island=plugin.getGrid().getIsland(targetPlayer);
  final IslandLevelEvent event=new IslandLevelEvent(targetPlayer,island,score);
  plugin.getServer().getPluginManager().callEvent(event);
}

Fixed version (ground truth):
@Override public void run(){
  int oldLevel=plugin.getPlayers().getIslandLevel(targetPlayer);
  plugin.getPlayers().setIslandLevel(targetPlayer,score);
  plugin.getPlayers().save(targetPlayer);
  if (plugin.getPlayers().inTeam(targetPlayer)) {
    for (    UUID member : plugin.getPlayers().getMembers(targetPlayer)) {
      plugin.getPlayers().setIslandLevel(member,score);
      plugin.getPlayers().save(member);
    }
  }
  if (sender != null) {
    if (!(sender instanceof Player)) {
      if (!report) {
        sender.sendMessage(ChatColor.GREEN + plugin.myLocale().islandislandLevelis + "String_Node_Str"+ ChatColor.WHITE+ plugin.getPlayers().getIslandLevel(targetPlayer));
      }
 else {
        for (        String line : reportLines) {
          sender.sendMessage(line);
        }
      }
    }
 else {
      if (!report) {
        if (plugin.getPlayers().getIslandLevel(targetPlayer) > oldLevel) {
          plugin.getMessages().tellOfflineTeam(targetPlayer,ChatColor.GREEN + plugin.myLocale(targetPlayer).islandislandLevelis + "String_Node_Str"+ ChatColor.WHITE+ plugin.getPlayers().getIslandLevel(targetPlayer));
        }
        if (sender instanceof Player && ((Player)sender).isOnline()) {
          String message=ChatColor.GREEN + plugin.myLocale(((Player)sender).getUniqueId()).islandislandLevelis + "String_Node_Str"+ ChatColor.WHITE+ plugin.getPlayers().getIslandLevel(targetPlayer);
          if (Settings.deathpenalty != 0) {
            message+="String_Node_Str" + plugin.myLocale(((Player)sender).getUniqueId()).levelDeaths.replace("String_Node_Str",String.valueOf(plugin.getPlayers().getDeaths(targetPlayer)));
          }
          sender.sendMessage(message);
          int requiredPoints=(Settings.levelCost * (plugin.getPlayers().getIslandLevel(targetPlayer) + 1 + levelHandicap)) - ((blocks * levelMultiplier) - (deathHandicap * Settings.deathpenalty));
          String toNextLevel=ChatColor.GREEN + plugin.myLocale(((Player)sender).getUniqueId()).islandrequiredPointsToNextLevel.replace("String_Node_Str",String.valueOf(requiredPoints));
          toNextLevel=toNextLevel.replace("String_Node_Str",String.valueOf(plugin.getPlayers().getIslandLevel(targetPlayer) + 1));
          sender.sendMessage(toNextLevel);
        }
      }
 else {
        if (((Player)sender).isOnline()) {
          for (          String line : reportLines) {
            sender.sendMessage(line);
          }
        }
      }
    }
  }
  if (plugin.getPlayers().inTeam(targetPlayer)) {
    UUID leader=plugin.getPlayers().getTeamLeader(targetPlayer);
    if (leader != null) {
      TopTen.topTenAddEntry(leader,score);
    }
  }
 else {
    TopTen.topTenAddEntry(targetPlayer,score);
  }
  Island island=plugin.getGrid().getIsland(targetPlayer);
  final IslandLevelEvent event=new IslandLevelEvent(targetPlayer,island,score);
  plugin.getServer().getPluginManager().callEvent(event);
}