Partial redistributing of 2-way matched invoice creates incorrect receipts

We created three different logged vouchers for items that were invoiced separately.  The PO had a single line with 6 units.  During the logged voucher redistribution, a single unit was selected for each of the vouchers.  The first voucher processed, correctly created a receipt for 1 unit, but the second voucher received 2 units and the third voucher received 3 units.

I then reversed the third distribution, but this did not put 3 units back on the PO. 

The AP Vouchers correctly show the units that have been vouchered, but P4314 does not have any units available to receive.  The line on the PO is not available for redistribution.  How do we fix this problem?