How To Fix VP444 - Function & is defined in the header and not deletable here

SAP Error Message - Details

• Message type: E = Error

• Message class: VP - Vertriebsbelegpartner

• Message number: 444

• Message text: Function & is defined in the header and not deletable here

What causes this issue?

Header partners cannot be deleted at item level.
INCLUDE 'NA_NO_PROCESSING_1' OBJECT DOKU ID TX LANGUAGE D

How to fix this error?

Delete the partner at header level.
If the <GL:partner function>partner function</> &V1& in
<GL:Customizing>Customizing</> is not defined as a compulsory function
for the document header and is marked as alterable, it can be deleted at
header level. The entries present at item level in this partner
function are then automatically deleted.

Error message extract from SAP system. Copyright SAP SE.