The Link between base and target document is broken when using 'Copy From' function

Hi all

One of my clients used 'Copy From' function to create GRPO from PO. However, the link between these two document is broken. The user does not have authorization to PO but GRPO only. It is not possible that the user would create a standalone GRPO. Our team have checked that the user did not duplicate any old GRPO.

Our team cannot reproduce the mentioned issue. So we are thinking if it is a system bug? Can we have some SAP notes for reference, please?

Our client is using 8.82 PL 12.

Many thanks for your help.