The bug occurs when a vendor has an active coupon. The seller orders from multiple vendors including the one with coupon and he enters the coupon. Until that stage everything seems alright. But on the order summary the total order price is deducted again. This is also the final price that is shown to the buyer.
Regular price: 299.80
Total price: 239.84
Shipping cost: 0 (no shipping configured)
Total price: 179.88
It seems that the coupon value is deducted twice. This only occures if shopping basket contains products from multiple vendeors where a signle vendor offers a coupon. This bug is critical in my opinion.
the site is not online because it is in a test/evaluation phase. But you can check it very easy yourself. Just order products from multiple vendors where one vendor has an active discount coupon. Apply that coupon and then check the final total price for that sub order.
I could do that for you on your demo, but Im not able to add sellers to the demo site…