https://userapps.support.sap.com/sap/support/knowledge/en/3200714
3200714 - PY-BE: error message when report RPCBWPB0 is executed in backgound | SAP Knowledge Base...
You get an error message in spool when running RPCBWPB0 in background: "An error occurred during printing (Message No. RP016 )"