9.1 upgrade testing create PO voucher from receiver is doubling the amount

AP currently adds invoice total on Invoice Information panel in header total box then copies in info from PO receiver, in 9.1 system is doubling the amount by adding a first row with the total figure in then copying info from receiver on an additional line, how do you prevent this doubling?  If they do not input the total they have no check figure that invoice and PO amount are equal and difference nets to zero as it does in 8.9