Error in BAPI BAPI_ACC_DOCUMENT_POST with vendor field XZEMP

Hi,

my problem is the same as the one described here:

https://answers.sap.com/questions/6262548/problem-using-bapi-bapiaccdocumentpost-with-vendor.html

The difference in my case is that it doesn't matter if field XZEMP is filled or not, I always receive the error message.

Can someone tell me how to bypass this error?

Thanks in advance and best regards,

Rodrigo