When applying prepayments to invoice, the entire invoice goes unaccounted

 Hello,

I have noticed a large number of invoices which were accounted earlier is showing up as unaccounted in the 'Unaccounted transactions report in Rel.12.1.1.

Upon further investigation, I am finding that the prepayment applied to these invoices is causing the entire invoice to be unaccounted.  When I look at the distribution for the invoice where the prepayment is applied, only the prepayment line is unaccounted which is forcing the entire invoice to be unaccounted.

I have gotten couple of GDF to fix some of them but what I can do to prevent these from happening further?

Regards, Joson.