Finally close PO for liberate funds

Summary:

Hi.

We use budget control for purchase orders.

Let's consider the following scenario:

A purchase order is issued for 100 USD.
For some reason, only 80 USD of the original 100 USD from the purchase order will be received and paid.
I understand that in order to release the remaining 20 USD from the budget, the purchase order needs to be definitively closed.

The problem is that when attempting to finally close the purchase order, the following error message appears: "You can't cancel or finally close this record because schedules with receipts pending delivery exist."

How can I release the funds in such cases?