No warning for incorrect payment set up with PayPal

As we talked about in IRC, there is no warning which says uc_coupon needs to have all items submitted as a single line to PayPal (configuration at admin/store/settings/payment/edit/methods). (Which means the coupon is not applied on the total amount that PayPal processes.)

I checked for errors at:
?q=admin/store (there are two notifications present: downloads and images)
?q=admin/store/customers/coupon (there are no notifications)

I am using uc_coupon 6.x-1.3 and Ubercart 6--2-0-RC6.

Thanks!