Program: 172820
Project: 172820
Buggy source:
@Listener public void onBlockPlace(ChangeBlockEvent.Place event,@Root Player player){
  if (!EagleFactions.AdminList.contains(player.getUniqueId())) {
    Optional<Faction> optionalPlayerFaction=FactionLogic.getFactionByPlayerUUID(player.getUniqueId());
    for (    Transaction<BlockSnapshot> transaction : event.getTransactions()) {
      World world=player.getWorld();
      if (MainLogic.getSafeZoneWorldNames().contains(world.getName()) && player.hasPermission(PluginPermissions.SAFE_ZONE_BUILD)) {
        return;
      }
      if (MainLogic.getWarZoneWorldNames().contains(world.getName()) && player.hasPermission(PluginPermissions.WAR_ZONE_BUILD)) {
        return;
      }
      Vector3i claim=transaction.getFinal().getLocation().get().getChunkPosition();
      Optional<Faction> optionalChunkFaction=FactionLogic.getFactionByChunk(world.getUniqueId(),claim);
      if (optionalChunkFaction.isPresent()) {
        if (optionalChunkFaction.get().Name.equals("String_Node_Str") && player.hasPermission(PluginPermissions.SAFE_ZONE_BUILD)) {
          return;
        }
 else         if (optionalChunkFaction.get().Name.equals("String_Node_Str") && player.hasPermission(PluginPermissions.WAR_ZONE_BUILD)) {
          return;
        }
 else         if (optionalPlayerFaction.isPresent()) {
          if (!FlagManager.canPlaceBlock(player,optionalPlayerFaction.get(),optionalChunkFaction.get())) {
            player.sendMessage(Text.of(PluginInfo.ErrorPrefix,PluginMessages.YOU_DONT_HAVE_PRIVILEGES_TO_DESTROY_BLOCKS_HERE));
            event.setCancelled(true);
          }
          return;
        }
 else {
          event.setCancelled(true);
          player.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.THIS_LAND_BELONGS_TO_SOMEONE_ELSE));
        }
      }
    }
  }
}

Fixed version (ground truth):
@Listener public void onBlockPlace(ChangeBlockEvent.Place event,@Root Player player){
  if (!EagleFactions.AdminList.contains(player.getUniqueId())) {
    Optional<Faction> optionalPlayerFaction=FactionLogic.getFactionByPlayerUUID(player.getUniqueId());
    for (    Transaction<BlockSnapshot> transaction : event.getTransactions()) {
      World world=player.getWorld();
      if (MainLogic.getSafeZoneWorldNames().contains(world.getName()) && player.hasPermission(PluginPermissions.SAFE_ZONE_BUILD)) {
        return;
      }
      if (MainLogic.getWarZoneWorldNames().contains(world.getName()) && player.hasPermission(PluginPermissions.WAR_ZONE_BUILD)) {
        return;
      }
      Vector3i claim=transaction.getFinal().getLocation().get().getChunkPosition();
      Optional<Faction> optionalChunkFaction=FactionLogic.getFactionByChunk(world.getUniqueId(),claim);
      if (optionalChunkFaction.isPresent()) {
        if (optionalChunkFaction.get().Name.equals("String_Node_Str") && player.hasPermission(PluginPermissions.SAFE_ZONE_BUILD)) {
          return;
        }
 else         if (optionalChunkFaction.get().Name.equals("String_Node_Str") && player.hasPermission(PluginPermissions.WAR_ZONE_BUILD)) {
          return;
        }
 else         if (optionalPlayerFaction.isPresent()) {
          if (!FlagManager.canPlaceBlock(player,optionalPlayerFaction.get(),optionalChunkFaction.get())) {
            player.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.YOU_DONT_HAVE_PRIVILEGES_TO_DESTROY_BLOCKS_HERE));
            event.setCancelled(true);
          }
          return;
        }
 else {
          event.setCancelled(true);
          player.sendMessage(Text.of(PluginInfo.ErrorPrefix,TextColors.RED,PluginMessages.THIS_LAND_BELONGS_TO_SOMEONE_ELSE));
        }
      }
    }
  }
}