I am having the same trouble. Cannot get Checkout page form field values to stay when someone selects Modify Info on Confirm Page to go back to Checkout. All fields are empty.
I can get the fields to remain populated when first filling out the form after a validation error, but after Checkout button is clicked the data is gone when go back
I have tried adding the Checkout Form to the Confirm page bindings and adding session variables but nothing works. Tried trigger as any form post and dynamically linking to form field. Nothing, blank fields when go back.
I have tried both session variables and dynamic text fields on the Checkout page to mimic the setup on the Confirm page. Nothing works and I am totally confusing myself!
Screen grabs attached