Unable to remove coupons from discount edit screen

When you create a new discount that uses coupons, you can create coupons within the discount screen itself, which is awesome. However, when you edit the discount later to remove some coupons that you no longer want associated with the discount (because we are re-using the same code on another discount), you can't remove the coupons from the discount edit screen. If you click "Remove" next to the coupon you want removed it disappears, then we save the discount itself. When you edit the discount again, the coupon is back in the list.

The only way I've found to remove a coupon from a discount is to edit the coupon and remove the discount reference from the discount entityreference field on the coupon itself. This is fine, but not quite as intuitive for users that are used to working within the discount screen for all coupon edits.