Program: 46879
Project: 46879
Buggy source:
@Override public void onEntityDamage(EntityDamageEvent event){
  if (event.getEntity() instanceof Wolf) {
    Wolf wolf=(Wolf)event.getEntity();
    if (wolf.isTamed()) {
      if (event instanceof EntityDamageByEntityEvent && wolf.getOwner() instanceof Player) {
        EntityDamageByEntityEvent damageEvent=(EntityDamageByEntityEvent)event;
        Player owner=(Player)wolf.getOwner();
        if (damageEvent.getDamager().equals(owner) && owner.getItemInHand().getType() == Material.BONE) {
          wolf.setOwner(null);
          wolf.setSitting(false);
          owner.sendMessage(ChatColor.RED + "String_Node_Str");
        }
 else         if (damageEvent.getDamager() instanceof Player) {
          Player attacker=(Player)damageEvent.getDamager();
          if (attacker.isOp() && attacker.getItemInHand().getType() == Material.BONE) {
            if (!owner.isOp()) {
              wolf.setOwner(null);
              wolf.setSitting(false);
              attacker.sendMessage(ChatColor.RED + "String_Node_Str" + owner.getDisplayName()+ "String_Node_Str");
              if (owner.isOnline())               owner.sendMessage(ChatColor.RED + attacker.getDisplayName() + "String_Node_Str");
            }
 else {
              attacker.sendMessage(ChatColor.RED + "String_Node_Str");
            }
          }
        }
      }
      event.setCancelled(true);
    }
  }
  if (event.getEntity() instanceof Player && event instanceof EntityDamageByEntityEvent) {
    Player player=(Player)event.getEntity();
    EntityDamageByEntityEvent damageEvent=(EntityDamageByEntityEvent)event;
    if (damageEvent.getDamager() instanceof Wolf) {
      Wolf wolf=(Wolf)damageEvent.getDamager();
      if (wolf.isTamed() && wolf.getOwner() instanceof Player) {
        Player owner=(Player)wolf.getOwner();
        if (owner.equals(player)) {
          wolf.setTarget(null);
          event.setCancelled(true);
        }
      }
    }
    if (damageEvent.getDamager().equals(damageEvent.getEntity()))     event.setCancelled(true);
  }
}

Fixed version (ground truth):
@Override public void onEntityDamage(EntityDamageEvent event){
  if (event.getEntity() instanceof Wolf) {
    Wolf wolf=(Wolf)event.getEntity();
    if (wolf.isTamed()) {
      if (event instanceof EntityDamageByEntityEvent && wolf.getOwner() instanceof Player) {
        EntityDamageByEntityEvent damageEvent=(EntityDamageByEntityEvent)event;
        Player owner=(Player)wolf.getOwner();
        if (damageEvent.getDamager().equals(owner) && owner.getItemInHand().getType() == Material.BONE) {
          wolf.setOwner(null);
          wolf.setSitting(false);
          owner.sendMessage(ChatColor.RED + "String_Node_Str");
        }
 else         if (damageEvent.getDamager() instanceof Player) {
          Player attacker=(Player)damageEvent.getDamager();
          if (attacker.isOp() && attacker.getItemInHand().getType() == Material.BONE) {
            if (!owner.isOp()) {
              wolf.setOwner(null);
              wolf.setSitting(false);
              attacker.sendMessage(ChatColor.RED + "String_Node_Str" + owner.getDisplayName()+ "String_Node_Str");
              if (owner.isOnline())               owner.sendMessage(ChatColor.RED + attacker.getDisplayName() + "String_Node_Str");
            }
 else {
              attacker.sendMessage(ChatColor.RED + "String_Node_Str");
            }
          }
        }
      }
      event.setCancelled(true);
    }
  }
  if (event.getEntity() instanceof Player && event instanceof EntityDamageByEntityEvent) {
    EntityDamageByEntityEvent damageEvent=(EntityDamageByEntityEvent)event;
    if (damageEvent.getDamager().equals(damageEvent.getEntity()))     event.setCancelled(true);
  }
}