Program: 80904
Project: 80904
Buggy source:
private void parseAutoFillplayers(final ProxiedPlayer player,List<Section> sectionList){
  for (int i=0; i < sectionList.size(); i++) {
    Section section=sectionList.get(i);
    if (section instanceof AutoFillPlayers) {
      sectionList.remove(i);
      String prefix=((AutoFillPlayers)section).prefix;
      String suffix=((AutoFillPlayers)section).suffix;
      int maxPlayers=((AutoFillPlayers)section).maxPlayers;
      List<String> sortRules=((AutoFillPlayers)section).sortRules;
      Skin skin=((AutoFillPlayers)section).skin;
      Map<String,ServerInfo> servers=ProxyServer.getInstance().getServers();
      Set<String> serverSet=new HashSet<>(servers.keySet());
      HashMultimap<String,String> aliasToServerMap=HashMultimap.create();
      for (      Map.Entry<String,String> entry : BungeeTabListPlus.getInstance().getConfigManager().getMainConfig().serverAlias.entrySet()) {
        if (ProxyServer.getInstance().getServerInfo(entry.getKey()) == null) {
          BungeeTabListPlus.getInstance().getLogger().warning("String_Node_Str" + entry.getKey() + "String_Node_Str");
          continue;
        }
        aliasToServerMap.put(entry.getValue(),entry.getKey());
      }
      List<String> list=new ArrayList<>();
      while (!serverSet.isEmpty()) {
        String server=serverSet.iterator().next();
        String alias=BungeeTabListPlus.getInstance().getConfigManager().getMainConfig().serverAlias.get(server);
        if (alias != null) {
          Set<String> strings=aliasToServerMap.get(alias);
          serverSet.removeAll(strings);
          list.add(Joiner.on(',').join(strings));
        }
 else {
          serverSet.remove(server);
          list.add(server);
        }
      }
      Collections.sort(list,new Comparator<String>(){
        @Override public int compare(        String s1,        String s2){
          int p1=plugin.getPlayerManager().getServerPlayerCount(s1,player,plugin.getConfigManager().getMainConfig().showPlayersInGamemode3);
          int p2=plugin.getPlayerManager().getServerPlayerCount(s2,player,plugin.getConfigManager().getMainConfig().showPlayersInGamemode3);
          if (p1 < p2) {
            return 1;
          }
          if (p1 > p2) {
            return -1;
          }
          return s1.compareTo(s2);
        }
      }
);
      int j=i;
      for (      String server : list) {
        if (showEmptyGroups || plugin.getPlayerManager().getPlayerCount(server,player,plugin.getConfigManager().getMainConfig().showPlayersInGamemode3) > 0) {
          try {
            List<Section> sections=parser.parseServerSections(prefix,suffix,skin,new ArrayList<>(0),server,sortRules,maxPlayers);
            for (            Section s : sections) {
              sectionList.add(j++,s);
            }
          }
 catch (          ParseException ex) {
            BungeeTabListPlus.getInstance().reportError(ex);
          }
        }
      }
    }
  }
}

Fixed version (ground truth):
private void parseAutoFillplayers(final ProxiedPlayer player,List<Section> sectionList,TabListContext context){
  for (int i=0; i < sectionList.size(); i++) {
    Section section=sectionList.get(i);
    if (section instanceof AutoFillPlayers) {
      sectionList.remove(i);
      String prefix=((AutoFillPlayers)section).prefix;
      String suffix=((AutoFillPlayers)section).suffix;
      int maxPlayers=((AutoFillPlayers)section).maxPlayers;
      List<String> sortRules=((AutoFillPlayers)section).sortRules;
      Skin skin=((AutoFillPlayers)section).skin;
      Map<String,ServerInfo> servers=ProxyServer.getInstance().getServers();
      Set<String> serverSet=new HashSet<>(servers.keySet());
      HashMultimap<String,String> aliasToServerMap=HashMultimap.create();
      for (      Map.Entry<String,String> entry : BungeeTabListPlus.getInstance().getConfigManager().getMainConfig().serverAlias.entrySet()) {
        if (ProxyServer.getInstance().getServerInfo(entry.getKey()) == null) {
          BungeeTabListPlus.getInstance().getLogger().warning("String_Node_Str" + entry.getKey() + "String_Node_Str");
          continue;
        }
        aliasToServerMap.put(entry.getValue(),entry.getKey());
      }
      List<String> list=new ArrayList<>();
      while (!serverSet.isEmpty()) {
        String server=serverSet.iterator().next();
        String alias=BungeeTabListPlus.getInstance().getConfigManager().getMainConfig().serverAlias.get(server);
        if (alias != null) {
          Set<String> strings=aliasToServerMap.get(alias);
          serverSet.removeAll(strings);
          list.add(Joiner.on(',').join(strings));
        }
 else {
          serverSet.remove(server);
          list.add(server);
        }
      }
      Collections.sort(list,new Comparator<String>(){
        @Override public int compare(        String s1,        String s2){
          int p1=context.getPlayerManager().getServerPlayerCount(s1,player,plugin.getConfigManager().getMainConfig().showPlayersInGamemode3);
          int p2=context.getPlayerManager().getServerPlayerCount(s2,player,plugin.getConfigManager().getMainConfig().showPlayersInGamemode3);
          if (p1 < p2) {
            return 1;
          }
          if (p1 > p2) {
            return -1;
          }
          return s1.compareTo(s2);
        }
      }
);
      int j=i;
      for (      String server : list) {
        if (showEmptyGroups || context.getPlayerManager().getPlayerCount(server,player,plugin.getConfigManager().getMainConfig().showPlayersInGamemode3) > 0) {
          try {
            List<Section> sections=parser.parseServerSections(prefix,suffix,skin,new ArrayList<>(0),server,sortRules,maxPlayers);
            for (            Section s : sections) {
              sectionList.add(j++,s);
            }
          }
 catch (          ParseException ex) {
            BungeeTabListPlus.getInstance().reportError(ex);
          }
        }
      }
    }
  }
}