Problem in third Party PR

Hi all

One Third Party PR -4********** of Quantity-65.000,000 was created against Sales Order-4******.User Created one Partial PO-6******01 of quantity-18.000,000.

User facing below error at the time of creation second PO for partial quantity against same PR.

Message No.06 249 Material for Preq & , Item &, already partially ordered.

As per standard SAP functionality we can not create more than one Partial PO against PR created from sales order.

But after removing fixed vendor, and info record from PR system allowing to create more than one Partial PO from same PR. User asking why system behaved like that???

why system allowing to create more than one PO from single PR in Third Party process.???

Thanks & Regards,

Bubai