Program: 7528
Project: 7528
Buggy source:
@Override public void onPlayerInteract(PlayerInteractEvent event){
  if (event.isCancelled()) {
    return;
  }
  Player player=event.getPlayer();
  Block myBlock=event.getClickedBlock();
  if (myBlock.getTypeId() == 54 && plugin.chestMachine.openChest(player,myBlock) == true) {
    player.sendMessage(ChatColor.GREEN + "String_Node_Str");
    return;
  }
 else   if (event.getClickedBlock().getTypeId() == 54) {
    player.sendMessage(ChatColor.RED + "String_Node_Str");
    event.setCancelled(true);
    return;
  }
  if ((event.getClickedBlock().getType() != Material.CHEST && event.getClickedBlock().getType() != Material.WORKBENCH && event.getClickedBlock().getType() != Material.FURNACE && event.getClickedBlock().getType() != Material.DISPENSER && event.getClickedBlock().getType() != Material.STONE_BUTTON && event.getClickedBlock().getType() != Material.LEVER && event.getClickedBlock().getType() != Material.WOODEN_DOOR && event.getClickedBlock().getType() != Material.IRON_DOOR_BLOCK && event.getClickedBlock().getType() != Material.FIRE && event.getClickedBlock().getType() != Material.CAKE_BLOCK)) {
    if (!event.hasItem()) {
      return;
    }
    if (event.getItem().getType() == Material.FENCE) {
      Block b=event.getClickedBlock().getFace(event.getBlockFace(),1);
      if (b.getTypeId() == 0) {
        BlockState oldState=b.getState();
        b.setType(event.getItem().getType());
        BlockPlaceEvent placeEvent=new BlockPlaceEvent(b,oldState,event.getClickedBlock(),event.getItem(),event.getPlayer(),true);
        plugin.getServer().getPluginManager().callEvent(placeEvent);
        if (placeEvent.isCancelled() || !placeEvent.canBuild()) {
          b.setType(oldState.getType());
          b.setData(oldState.getData().getData());
        }
 else {
          int amnt=event.getItem().getAmount();
          if (amnt > 1)           event.getItem().setAmount(amnt - 1);
 else           event.getPlayer().getInventory().remove(event.getItem());
        }
      }
    }
  }
}

Fixed version (ground truth):
@Override public void onPlayerInteract(PlayerInteractEvent event){
  if (event.isCancelled()) {
    return;
  }
  Player player=event.getPlayer();
  Block myBlock=event.getClickedBlock();
  if (myBlock.getTypeId() == 54 && plugin.chestMachine.openChest(player,myBlock) == true) {
    player.sendMessage(ChatColor.GREEN + "String_Node_Str");
    return;
  }
 else   if (event.getClickedBlock().getTypeId() == 54) {
    player.sendMessage(ChatColor.RED + "String_Node_Str");
    event.setCancelled(true);
    return;
  }
  if (event.getAction() == Action.RIGHT_CLICK_AIR || event.getAction() == Action.RIGHT_CLICK_BLOCK) {
    if ((event.getClickedBlock().getType() != Material.CHEST && event.getClickedBlock().getType() != Material.WORKBENCH && event.getClickedBlock().getType() != Material.FURNACE && event.getClickedBlock().getType() != Material.DISPENSER && event.getClickedBlock().getType() != Material.STONE_BUTTON && event.getClickedBlock().getType() != Material.LEVER && event.getClickedBlock().getType() != Material.WOODEN_DOOR && event.getClickedBlock().getType() != Material.IRON_DOOR_BLOCK && event.getClickedBlock().getType() != Material.FIRE && event.getClickedBlock().getType() != Material.CAKE_BLOCK)) {
      if (!event.hasItem()) {
        return;
      }
      if (event.getItem().getType() == Material.FENCE) {
        Block b=event.getClickedBlock().getFace(event.getBlockFace(),1);
        if (b.getTypeId() == 0) {
          BlockState oldState=b.getState();
          b.setType(event.getItem().getType());
          BlockPlaceEvent placeEvent=new BlockPlaceEvent(b,oldState,event.getClickedBlock(),event.getItem(),event.getPlayer(),true);
          plugin.getServer().getPluginManager().callEvent(placeEvent);
          if (placeEvent.isCancelled() || !placeEvent.canBuild()) {
            b.setType(oldState.getType());
            b.setData(oldState.getData().getData());
          }
 else {
            int amnt=event.getItem().getAmount();
            if (amnt > 1)             event.getItem().setAmount(amnt - 1);
 else             event.getPlayer().getInventory().remove(event.getItem());
          }
        }
      }
    }
  }
}