Discount miscalcultaion with multiple discounts and multi-price tickets

I’ve got a problem with discount calculation.

There are two prices (multi-price setup). One for children 10 € and one for adults 15 €.
Early Bird Tickets get a discount: Children 5 Euros, Adults 3 Euros.

There is a multi-seat setup. For children and for adults.

There are TWO discount fields setup. One for children code, one for adults code. Fixed per seat.

If you book ONE ticket for children and add the code for children, calculation is ok.
If you book ONE ticket for adults and add the code for adults, calculation is ok.
If you book ONE ticket for children and ONE for adult and add the code for children and the code for adults in second discount field, calculation is wrong.

But the codes are valid for either, children or adult prices.

I don’t know how to tell EME that if ou enter in upper discount field that it belongs to children pricing and the lower discount field to adult pricing.

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