Hi,
I think I've figured out the problem. Did you create and save a separate Seller Details for each of the distinct sections, e.g.
one for Payment
one for Shipping
one for Terms of Sale
....and not a composite (single) Sellers Details with all the sections?
That method won't work and why you're having the selection problem on the one-page. You need to fill-in all the tabbed sections needed when you create a Seller Details and therefore select only one to get all on the one-page lister.
If you have other unique combinations of Seller Details language for some listing item, then you create a new Named Seller Details for that combination.
Hope that makes sense.
Danno