Problem with orders en orderdetails

I created a shop in ecart5, it works fine, I thought. I must do something wrong, because when I tested the shop by buying a product and made the payment, it works well. Then I login again and want to buy the same product, the old order and orderdetail will be rewritten in the database. Instead of 2 orders there is only one. The orderdetail get a new ID and the old is deleted. All data is updated. The order ID stays the same. I put the shop behind an inlog. I tried everything last 2 days, In the cart I changed in the bindings; ignore, add new, and replace. Checked the DB, checked in confirm the order en orderdetails. I just bought ecart5, 1 week, please help.