We use discount codes so users can purchase 'pre-paid' products. They purchase a pass for 100, 50, 25, ... workshops and receive a discount code valid 100, 50, 25, ... times on our workshops.

The codes are set up as:
100% discount
Apply to all matching products
Restrict by date
Maximum number of redemptions (per code): 100 (or 50 or 25...)
Applicable Product class: Sloan-C workshop

When someone purchases in the same order multiple workshops (x different ones or x times the same ones for different registrants) the total discount is
correct but only 1 use of the code is recorded instead of x uses.

Is this a bug or do I set up my code incorrectly?

We use:
Drupal 6
Ubercart 6.x-2.9
Discount Coupon purchase 6.x.1.7
Discount Coupons 6.x.1.7

Thanks fo your help.