Goal - counting double after a second entry

Hi,

I had an 'order-received' goal reached (correctly),
but after 30 min, the user returned to the 'order-received' page and for some reason is was considered a new visit and counted the goal again.
It was from the same ip, same user id, same everything.
The goal is set up as not to count more then once.
Any idea how to correct this ?

THANKS !