Program: 158561
Project: 158561
Buggy source:
private boolean performUserCommand(User user,String message,UUID chatId){
  String command=message.substring(1).trim().toUpperCase(Locale.ENGLISH);
  if (command.startsWith("String_Node_Str") || command.startsWith("String_Node_Str")) {
    message=UserManager.getInstance().getUserHistory(message.substring(command.startsWith("String_Node_Str") ? 3 : 9));
    chatSessions.get(chatId).broadcastInfoToUser(user,message);
    return true;
  }
  if (command.startsWith("String_Node_Str") || command.startsWith("String_Node_Str")) {
    String rest=message.substring(command.startsWith("String_Node_Str") ? 3 : 9);
    int first=rest.indexOf("String_Node_Str");
    if (first > 1) {
      String userToName=rest.substring(0,first);
      rest=rest.substring(first + 1).trim();
      User userTo=UserManager.getInstance().getUserByName(userToName);
      if (userTo != null) {
        if (!chatSessions.get(chatId).broadcastWhisperToUser(user,userTo,rest)) {
          message+=new StringBuilder("String_Node_Str").append(userToName).append("String_Node_Str").toString();
          chatSessions.get(chatId).broadcastInfoToUser(user,message);
        }
      }
 else {
        message+=new StringBuilder("String_Node_Str").append(userToName).append("String_Node_Str").toString();
        chatSessions.get(chatId).broadcastInfoToUser(user,message);
      }
      return true;
    }
  }
  if (command.equals("String_Node_Str") || command.equals("String_Node_Str")) {
    message+=new StringBuilder("String_Node_Str").append("String_Node_Str").append("String_Node_Str").append("String_Node_Str").toString();
    chatSessions.get(chatId).broadcastInfoToUser(user,message);
    return true;
  }
  return false;
}

Fixed version (ground truth):
private boolean performUserCommand(User user,String message,UUID chatId,boolean doError){
  String command=message.substring(1).trim().toUpperCase(Locale.ENGLISH);
  if (doError) {
    message+=new StringBuilder("String_Node_Str" + message + "String_Node_Str").append("String_Node_Str").append("String_Node_Str").append("String_Node_Str").append("String_Node_Str").toString();
    chatSessions.get(chatId).broadcastInfoToUser(user,message);
    return true;
  }
  if (command.startsWith("String_Node_Str") || command.startsWith("String_Node_Str")) {
    message=UserManager.getInstance().getUserHistory(message.substring(command.startsWith("String_Node_Str") ? 3 : 9));
    chatSessions.get(chatId).broadcastInfoToUser(user,message);
    return true;
  }
  if (command.startsWith("String_Node_Str") || command.startsWith("String_Node_Str")) {
    String rest=message.substring(command.startsWith("String_Node_Str") ? 3 : 9);
    int first=rest.indexOf("String_Node_Str");
    if (first > 1) {
      String userToName=rest.substring(0,first);
      rest=rest.substring(first + 1).trim();
      User userTo=UserManager.getInstance().getUserByName(userToName);
      if (userTo != null) {
        if (!chatSessions.get(chatId).broadcastWhisperToUser(user,userTo,rest)) {
          message+=new StringBuilder("String_Node_Str").append(userToName).append("String_Node_Str").toString();
          chatSessions.get(chatId).broadcastInfoToUser(user,message);
        }
      }
 else {
        message+=new StringBuilder("String_Node_Str").append(userToName).append("String_Node_Str").toString();
        chatSessions.get(chatId).broadcastInfoToUser(user,message);
      }
      return true;
    }
  }
  if (command.equals("String_Node_Str") || command.equals("String_Node_Str")) {
    message+=new StringBuilder("String_Node_Str").append("String_Node_Str").append("String_Node_Str").append("String_Node_Str").toString();
    chatSessions.get(chatId).broadcastInfoToUser(user,message);
    return true;
  }
  return false;
}