NAV 2016 - Purchase order created from Blanket PO and Deletion of Purchase Order

Hello - 

I have a purchase order that is created from the Blanket PO. On the Purchase order lines I have Blanket PO No. and Blanket PO Line no. filled in. I have now completed received and invoiced the Purchase order matching the quantity specified on the Blanket PO. Even though I have fully received and invoiced the quantity my Purchase order is still open and is not deleted. There is absolutely no customizations carried out. We are using Dynamics Nav 2016 CU 9. Is there any hotfix for this issue.

Any help is highly appreciated.