1. Do a fresh install
2. Add Product X to your cart
3. Start checkout and go up to the confirmation page
4. Go back and add Product Y to your cart
5. Go again up to the confirmation page.
6. Log Out of OPC
7. Click on products ordered under "my account" as a customer and it will tell you that you have ordered two pieces of Product X and one of Product Y when actually you have not ordered anything.
Similarly on the admin side, OPC will tell you two pieces of Product X and one of Product Y have been ordered when nothing has been. Putting a filter on the admin will not cure the problem because firstly, the items have a pending status and secondly, it is just treating the symptom rather than the problem.
I have just done what you have said and no orders appear. The only time the orders will apear is if I click the checkout confirm button and leave the web site.
Is that what you mean click the checkout confirm button?