Add to cart redirecting to homepage

-- url of the page with the problem -- : www.ultimahub.com/Our-Categories/categor...y-setup-shanghai-ftz
-- HikaShop version -- : 2.4.0
-- Joomla version -- : 3.4.0
-- PHP version -- : 5.5.21
-- Browser(s) name and version -- : ie firefox chrome safari

Great component however we are experiencing a very annoying bug.
We can add one item to the cart however if we try adding a few items to the cart and always if we try and add an item that is already in the cart again we get redirected to the homepage.
To view this issue:
Please click here: www.ultimahub.com/Our-Categories/categor...y-setup-shanghai-ftz
1) Please click on “add to cart” for Shanghai Free Trade Zone-WFOE Setup and then once added to the cart click “add to cart” it again to add it twice. You will be redirected to the homepage.
2) Also if a few items are clicked on and added to cart. Soon you will be redirected to the homepage.

Please notice the homepage url in the attached picture also. It is showing as the popup url.

Can you please help us fix this asap.
Many thanks