Program: 172826
Project: 172826
Buggy source:
@Override public CommandResult execute(CommandSource source,CommandContext context) throws CommandException {
  Optional<String> optionalFactionName=context.<String>getOne("String_Node_Str");
  if (optionalFactionName.isPresent()) {
    if (source instanceof Player) {
      Player player=(Player)source;
      String rawFactionName=optionalFactionName.get();
      if (FactionLogic.getFactionName(player.getUniqueId()) == null) {
        String factionName=FactionLogic.getRealFactionName(rawFactionName);
        if (factionName == null) {
          player.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.THERE_IS_NO_FACTION_CALLED + "String_Node_Str",TextColors.GOLD,rawFactionName + "String_Node_Str"));
          return CommandResult.success();
        }
 else {
          if (EagleFactions.AdminList.contains(player.getUniqueId())) {
            FactionLogic.joinFaction(player.getUniqueId(),factionName);
            source.sendMessage(Text.of(PluginInfo.PluginPrefix,TextColors.GREEN,PluginMessages.SUCCESSFULLY_JOINED_FACTION + "String_Node_Str",TextColors.GOLD,factionName));
            return CommandResult.success();
          }
          for (          Invite invite : EagleFactions.InviteList) {
            if (invite.getPlayerUUID().equals(player.getUniqueId()) && invite.getFactionName().equals(factionName)) {
              try {
                if (MainLogic.isPlayerLimit()) {
                  int playerCount=0;
                  Faction faction=FactionLogic.getFaction(factionName);
                  playerCount+=faction.Leader.equals("String_Node_Str") ? 0 : 1;
                  playerCount+=faction.Officers.isEmpty() ? 0 : faction.Officers.size();
                  playerCount+=faction.Members.isEmpty() ? 0 : faction.Members.size();
                  if (playerCount >= MainLogic.getPlayerLimit()) {
                    player.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.YOU_CANT_JOIN_THIS_FACTION_BECAUSE_IT_REACHED_ITS_PLAYER_LIMIT));
                    return CommandResult.success();
                  }
                }
                FactionLogic.joinFaction(player.getUniqueId(),factionName);
                EagleFactions.InviteList.remove(new Invite(factionName,player.getUniqueId()));
                source.sendMessage(Text.of(PluginInfo.PluginPrefix,TextColors.GREEN,PluginMessages.SUCCESSFULLY_JOINED_FACTION + "String_Node_Str",TextColors.GOLD,factionName));
                return CommandResult.success();
              }
 catch (              Exception exception) {
                exception.printStackTrace();
              }
            }
          }
          source.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.YOU_HAVENT_BEEN_INVITED_TO_THIS_FACTION));
        }
      }
 else {
        source.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.YOU_ARE_ALREADY_IN_A_FACTION));
      }
    }
 else {
      source.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.ONLY_IN_GAME_PLAYERS_CAN_USE_THIS_COMMAND));
    }
  }
 else {
    source.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.WRONG_COMMAND_ARGUMENTS));
    source.sendMessage(Text.of(TextColors.RED,PluginMessages.USAGE + "String_Node_Str"));
  }
  return CommandResult.success();
}

Fixed version (ground truth):
@Override public CommandResult execute(CommandSource source,CommandContext context) throws CommandException {
  Optional<String> optionalFactionName=context.<String>getOne("String_Node_Str");
  if (optionalFactionName.isPresent()) {
    if (source instanceof Player) {
      Player player=(Player)source;
      String rawFactionName=optionalFactionName.get();
      if (FactionLogic.getFactionName(player.getUniqueId()).equals("String_Node_Str")) {
        String factionName=FactionLogic.getRealFactionName(rawFactionName);
        if (factionName == null) {
          player.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.THERE_IS_NO_FACTION_CALLED + "String_Node_Str",TextColors.GOLD,rawFactionName + "String_Node_Str"));
          return CommandResult.success();
        }
 else {
          if (EagleFactions.AdminList.contains(player.getUniqueId())) {
            FactionLogic.joinFaction(player.getUniqueId(),factionName);
            source.sendMessage(Text.of(PluginInfo.PluginPrefix,TextColors.GREEN,PluginMessages.SUCCESSFULLY_JOINED_FACTION + "String_Node_Str",TextColors.GOLD,factionName));
            return CommandResult.success();
          }
          for (          Invite invite : EagleFactions.InviteList) {
            if (invite.getPlayerUUID().equals(player.getUniqueId()) && invite.getFactionName().equals(factionName)) {
              try {
                if (MainLogic.isPlayerLimit()) {
                  int playerCount=0;
                  Faction faction=FactionLogic.getFaction(factionName);
                  playerCount+=faction.Leader.equals("String_Node_Str") ? 0 : 1;
                  playerCount+=faction.Officers.isEmpty() ? 0 : faction.Officers.size();
                  playerCount+=faction.Members.isEmpty() ? 0 : faction.Members.size();
                  if (playerCount >= MainLogic.getPlayerLimit()) {
                    player.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.YOU_CANT_JOIN_THIS_FACTION_BECAUSE_IT_REACHED_ITS_PLAYER_LIMIT));
                    return CommandResult.success();
                  }
                }
                FactionLogic.joinFaction(player.getUniqueId(),factionName);
                EagleFactions.InviteList.remove(new Invite(factionName,player.getUniqueId()));
                source.sendMessage(Text.of(PluginInfo.PluginPrefix,TextColors.GREEN,PluginMessages.SUCCESSFULLY_JOINED_FACTION + "String_Node_Str",TextColors.GOLD,factionName));
                return CommandResult.success();
              }
 catch (              Exception exception) {
                exception.printStackTrace();
              }
            }
          }
          source.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.YOU_HAVENT_BEEN_INVITED_TO_THIS_FACTION));
        }
      }
 else {
        source.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.YOU_ARE_ALREADY_IN_A_FACTION));
      }
    }
 else {
      source.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.ONLY_IN_GAME_PLAYERS_CAN_USE_THIS_COMMAND));
    }
  }
 else {
    source.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.WRONG_COMMAND_ARGUMENTS));
    source.sendMessage(Text.of(TextColors.RED,PluginMessages.USAGE + "String_Node_Str"));
  }
  return CommandResult.success();
}