Sorry Nicolas,
I tested all 3 types of behavious, found only 1st type working if a discount item added in the cart. It will add coupon value additional on discounted price. 2nd type and 3rd type don't works either if there is a discount item added in the cart, even there are some other item(s) not in discount, coupon will not work for all.
Example 1st image, coupon for a non discount item, it works:
After added a discount item (top one), both not work - no coupon discount either
My coupon are apply to all categories, the individual discount item are also in these categories. But I have added these discount items in a separate "On Sale" category that the coupon not apply to it. Is this the issue?
Hope this is clear, please advice.
Thank You!