Stackable variants Bug

[Giladd]

Hello to the Virtuemart Team,

I think there is a bug in the "Stackable variants". When I change the quantity from 1 to 2 (with the + sign) the quantity add 2 instead of 1. It happens only with products that have chilled products and when I disable the "Stackable variants" plug in it working OK.

Please take a look here http://buycycle.co.il/bicycle-apparel-shoes/bicycle-socks/comfit-socks-white-buycycle

I hope I explain the problem properly.
Please advice.