Problem after update to 2.1.0

Hi Nicolas,
Just update my hikashop without make previosly backup...
After some hours of intense search in forum, I am asked for you help.
Now, I have one bug(?) and BIG problem.
Possible bug - after make order and pass to payment, then product quanity is changed and refresh button clicked, this produced redirect to previosly configured page with message "Shopping cart is empty", so you must click again to updated "Total" in minicart module, for return to process order.
Resolved: I don`t know how...

And problem:
The price of product I always set with TAX. For example, 35,0000002. witout TAX 28,92562 (is autocalculated).
Now, then make order, "Total" field (of one item) showing 35,01, but "Total for pay" is 35,00.
And then change quanity for 10 item, "Total" field showing 350,05, and "Total for pay" is 295,37.
For example, try this product (sorry, is russian):
www.novodreams.com/rezerv/product/16-/category_pathway-12

Resolved: I was disable "HikaShop Custom Quantity tax plugin"

Thank you for quick responce!