Intermittent issue - PO Invoice from multiple receipts,splits into multiple invoices in AP

Intermittent.  Job related PO Invoice for multiple receipts entered using drop down, the invoice appears to be OK but after day end the AP Invoices are split by receipt number with the same Inv#.  This creates an Error batch in AP.  V 2017 -PU6; cannot replicate it. Seems to be only certain job types but cannot identify any differences. Tried in 2018-PU9 and 2019-PU4