I have an issue when creating a contact person thru CMD_EI_API=>MAINTAIN_BAPI.
It creates the contact person as expected in KNVK and also creates a Business Partner for it.
But it's skipping the step to create the business partner relationship in BUT051.
Does anyone have an idea how to solve this issue? When creating a contact person thru VD02 or VAP1 the business partners are correctly assigned.
This note seems to be related to your issue:
2924939 - Business Partner relationships are not created in BUT050 while using BAPI