Hi,
By looking at your order to Billing copy controls, it shows 001 for VBRK/VBRP. Generally, I have not seen anyone using this routine.
From Del to Bil copy control I could see something 601 for VBRK/VBRP.
Now, I request you to create a billing with reference OR and Del and provide us the split analysis. So that I can help you more.
Regards, Sai Krishna.