Packing HU multiple lines in delivery serialized part

I am not able to use one HU to pack a same serialized part in 2 lines on a delivery.

Line 10 : 2 Ea

Line 20 : 4 Ea

Trying to use a HU with quantity 6 no’s to pack .

System says not possible for serialized part.

It works for Non serialized parts.

How do I deal with this?

Any enhancements possible?