When I place a new (test) order, old orders are altered

[Bleepie]

Hi,

I have an issue where old orders are altered when new ones are placed. I placed 1 test order:

Order #1010 where the customer name is "Sjaak Trekhaak" I now placed another order, same address, same email, same product in the cart, only the name is different:

As you can see order #1010 is now altered. The name "Sjaak Trekhaak" is now "Sjon Beton". This is not acceptable.

Why is this happening and how can I fix this?

EDIT: I found out that using the same email is the cause of this:

I placed a new order where the name was "test collectie voor" and the email was the same as "Sjaak Trekhaak" and "Sjon Beton". Then I placed a new order where the name was "test collectie na" but this time I used a different email adres and you can see that doesn't change the other orders.

This must be a bug right? I don't want someone to screw up my orders if they know they can by using someone elses email adres.