[Demonstration 1]

[Buggy Method]
@SubscribeEvent(priority = EventPriority.LOWEST)
public void entityDropEvent(LivingDropsEvent e) {
    if (e.getEntity() instanceof EntityPlayer && e.getResult() != Event.Result.DENY && !e.getEntity().getEntityWorld().isRemote) {
        final EntityPlayer player = (EntityPlayer) e.getEntity();
        if (player.isSpectator())
            return;
        final World w = player.getEntityWorld();
        Map<ItemStack, EntityEquipmentSlot> cache = equipmentCache.computeIfAbsent(player, (EntityPlayer p) -> new HashMap<>());
        EntityLootableBody corpse = new EntityLootableBody(player);
        corpse.forceSpawn = true;
        corpse.setUserName(player.getName());
        corpse.setRotation(player.rotationYaw);
        NonNullList<ItemStack> items = NonNullList.<ItemStack>create();
        for (EntityItem itemEntity : e.getDrops()) {
            ItemStack item = itemEntity.getEntityItem();
            if (!item.isEmpty() && cache.containsKey(item)) {
                corpse.setItemStackToSlot(cache.get(item), item);
            } else if (!item.isEmpty()) {
                items.add(item);
            }
        }
        corpse.initializeItems(items);
        if (LootableBodies.addBonesToCorpse) {
            corpse.addItem(new ItemStack(Items.BONE, 1 + w.rand.nextInt(3)));
            corpse.addItem(new ItemStack(Items.ROTTEN_FLESH, 1 + w.rand.nextInt(3)));
        }
        w.spawnEntity(corpse);
        e.getDrops().clear();
    }
}

[Buggy Hunk]
ItemStack item = itemEntity.getEntityItem();

[Patch]
ItemStack item = itemEntity.getItem();

[Demonstration 2]

[Buggy Method]
public EntityItem drop(Entity entity, Item item, int meta, int amount, int chance) {
    ItemStack stack = new ItemStack(item, chance, 0);
    if (stack.getCount() > amount) {
        stack.setCount(amount);
    }
    EntityItem drop = new EntityItem(entity.getEntityWorld(), entity.posX, entity.posY, entity.posZ, stack);
    return drop;
}

[Buggy Hunk]
ItemStack stack = new ItemStack(item, chance, 0);

[Patch]
ItemStack stack = new ItemStack(item, chance, meta);

[Demonstration 3]

[Buggy Method]
@Override
public void buy(InventoryClickEvent event, Player player, ShopItem item) {
    ItemStack icon = item.getItem();
    int amt = event.getClick().isShiftClick() ? 64 : 1;
    if (!shop_infinite && icon.getAmount() < amt)
        amt = icon.getAmount();
    EconomyResponse response = economy.withdrawPlayer(player, item.getWorth() * amt);
    if (response.transactionSuccess()) {
        player.playSound(player.getLocation(), Util.getSound(sound_onShopUse), 1.0f, 1.0f);
        player.sendMessage("\u00A76You bought \u00A7e" + amt + "\u00A76 of \u00A7a" + icon.getType() + "\u00A76.");
        ItemStack reward = item.getCleanCopy();
        reward.setAmount(amt);
        player.getInventory().addItem(reward);
        if (!shop_infinite)
            item.getItem().setAmount(amt);
    } else {
        player.sendMessage("\u00A7cYou cannot buy this at the moment!");
    }
}

[Buggy Hunk]
item.getWorth() * amt);

[Patch]
item.getBuy() * amt);