Hi Khuliso,
Based on the behaviour you are describing it seems that there is a failure in the process chains which are being run when you are executing the upload to BI.
In RSA1 you will need to check the logs for the process chains for PO and Invoice. This is where you can see what step is failing in the process.
Can you present some additional information from the short dump?
Thank you,
Oluseun Otulaja