FM Account assignments are not inherited from the PO

Hi Experts,

This is an implementation project of SAP S/4HANA ON-PREMISE 1511. We have BCS active ( EA-PS Release 800 and 0001 SP).

We are testing and We get incorrect FM account assignment derivation from FMDERIVE when posting Good Recepts with reference to PO of internal order (Account Assignment F).

We are using the flags available in table FM01X, specifically FLG_PO_PROTECT, but We get the message that function is obsolete.

We need all documents to inherit FM account assignments from the PO.

What are my options?.

Thanks.