Taxes for variants in after upgrading to 2.4

-- HikaShop version -- : 2.4.0
-- Joomla version -- : 3.3.6
-- PHP version -- : 5.5.32
-- Browser(s) name and version -- : all
-- Error-message(debug-mod must be tuned on) -- : none

I have installed hikashop on 3 websites. 2 days ago I upgraded from 2.3.5 to 2.4, after installing pdf invoice plugin.

First I didn't notice the problem, because I tested the shops on product without variants, and all worked allright.

After that though, some clients ordered products with variants, and for each variant the chart added some abnormal ammount, like this:

Regardless the price of the product (only if it was with variants), in the chart was added the same price like the product price, like VAT. For example, if I would add a product with a 10RON price and a product with 30 RON price, the total price will be 10+30+ another 10 + another 30, both last sums being regarded like VAT.

Both problems were encountered on two websites, www.coloidale.ro and www.magazin.coloidale.ro . On the third website , www.vindemiere.ro , I tried to duplicate the problem, adding variants at some product, but I couldn't.

For now, I reverted to 2.3.5 version, and the websites are working, but this is not ok.

When you have time, I can reinstall 2.4 on one website, maybe you can figure where the problem is. Until reinstalling, you can't duplicate the error, so if you can't trace it in your files, please let me know to help you trace it on our website.