Unable to cancel AP Invoice which is related with Down Payment

[rmpal]

Dear Experts,

One of our client facing the issue like,

we have the Down Payment Rs. 19000

And we make AP invoice against GRPO with the amount Rs. 19000

While making AP Invoice we have knock off the Downpayment, So there is no due in AP Invoice, So invoice get closed after posting invoice, But the problem is, due to some technical reasons that DPM amount has gone into Discount filed. So the Downpayment amount is not reconcile with ap invoice,

So we are trying to cancel this ap invoice, But we have facing error "You cannot Cancel the AP invoice which is reconciled manually"

We have open Manage Previous Reconciliation screen, That particular Document does not have "Cancel Reconciliation" option it is disabled.

Now how can we cancel this ap inovice? Or any other possibilities are there to rectify this pending DPM.

Here I enclosed the Screen Shot for your reference.