on the Paymentconfirm.php page, there is a collection of hidden elements that passes the cart information to paypal.
in those hidden elements, there are elements for the billing info, it sounds like those are bound to the shipping elements from the Paymentcheckout.php page instead of the billing elements.
first remove the shipping elements from the checkout form.
on the confirm page, go to the bindings tab and click the plus button, select Form Data. For the form page, select the checkout page.
This will add dynamic bindings for the elements from the checkout page.
Now select each of the address hidden elements and bind it to the corresponding element from the checkout form group.