COPA Derivation for Partner functions

Hi Experts,

We are using S4HANA 1909. I have created a derivation rule for Partner functions End customer(ZF) and Sales Representative(Z1). These fields are populating in test mode in KEDR based on sales order number, But when I post delivery and Billing documents, these fields not populating in COPA document.

I have followed below steps.

1. I have created two characteristics for End customer(WW015) and Sales Representative(WW023).

2. Created 2 derivation steps for each characteristic as below.

End Customer

SOURCE FIELDS

VBPA-VBELN = COPA-KAUFN

VBPA-POSNR = COPA-KDPOS (selected Initial value allowed and Entire field content check box)

VBPA-PARVW = GLOBAL-USERTEMP1 (Specified Constant = SD Part Function(i.e.ZF)

TARGET FIELDS

VBPA-KUNNR = COPA-WW015

I have followed same procedure for Sales Representative but in Usertemp1 constant maintained as Z1 and target field as WW023.

this is working in test mode of KEDR based on sales Order, but during posting these are not flowing.

Could you let me know If I am missing something here??

Regards

Rafi