some of the product does not show next/prev button

myfinaltouchinc.com
username:custo2
password:custo2

I encountered problems in my products on tops categories.
The last 2 item does not show next/prev button when I clicked the item.
and also with the shadowbox when i clicked the image it won't appear on shadow box.

can you send me details on how can i fixed this?

I was tried to used shadow box, but it does not work if I trigered my variant changer javascript, i used another javascript to open all the images in new pop-up window,
I just want to know which code handles the update characteristic/variants because everytime I change the value in my product page i want only change product image and data excluding the add to cart input

because everytime I Mouseover I notice it refreshes including the add to cart quantity~ i just want to know what to delete to exclude that area from changing-
my characteristic div was hidden
I also notice during my check out tests, the back image of the product is the one shown in cart area how to avoid that?

Which PHP file do I need to override to be able to update my next/prev buttons for our website?
this is the website that has multiple custom fields per color of the product.

Thank you for the response I just update the whole version of the hikashop business edition, and override my previous changes
the updates really works and the item and arrow does not jump from one category to another the products unlike before, Thank you