I see you have removed the template tag [%thankyou_link%] from your Common Thank-you Email, which would normally insert a link to the buyer's thank-you/download page for all items in their purchase. Thus, buyers who don't proceed to their thank-you page after checkout (or who need another chance to download later) must get the link from the Product Thank-you Email we can send for each item they bought.
Thus, make sure you have not disabled the Product Thank-you Email for each product having the problem you reported -- e.g., in your own test order, I see one item does have the Product Thank-you Email enabled whereas the other does not, so that would explain why you did not receive an emailed link for that latter item.
