User WF-BATCH and BAPI_PO_RELEASE does not work without printer assigned

Hello Gurus,

The function BAPI_PO_RELEASE is used in our PO approval workflow, but this one does not work till the user WF_BATCH has no printer defined in USR01-SPLD. This is a strange behavior because the output message assigned to the PO has a message transmission medium equals to 5 (External send) => not print.

Does someone have already met the same issue?

How this could be solved without assigning a default printer to user WF_BATCH?

Kind regards

Chris