Update buuton in cart product list

[jordantsap]

Hello everybody.
I'm working on a joomla 2.5 platform with VirtueMart 2.6.12.2. in a test server.
I have the following problem:
A developer added a new price field for "gift wrapping" in product details, it's displayed in the product description and in the cart product list, the arrows succesfully increase and decrease the quantity, but the cart cannot be updated in the cart item list section clicking the update button.
The custom field can be updated into the product details section but it cannot be updated in the cart section.
The update button also works nice for the core quantity but not for the custom.
Where and what should i look? Is the solution to js files or php?
Bellow i attached the files that are related to the cart section but if you need another file too just ask me to.