How to delete attachament from purchase order lines

In Oracle Fusion Procurement, we have the following issue and requirement:

We are unable to delete attachments from Purchase Order lines. When attempting to remove them, the system returns the following error message:
“You don’t have the permission to delete these files.”

Purchase Order lines include attachments inherited from the Blanket Purchase Agreement, and the system currently does not allow their deletion.

Request:
How can attachments be removed from a Purchase Order?

Thanks,

Lorenzo