Thanks Jiju for a long and prompt reply.
Issue method is Manual.
Regarding scenario, I have already given in my reply. Though please find the same again as follow:
There is a item for which Planned Qty is 100 but issued qty is 105 and in another item Planned Qty is 105 but issued 100, and no other issues and receipts pending.
I have changed Planned Qty as Issue Qty also to close Prod Order but it does not allow me to close.