Purchasing Receiving Issue

I have a real conundrum.  Since our last patch cycle, our users have experienced an intermittent issue doing purchasing receipts thru forms.  Multi-line receipts don't always transact all lines, as an example 8 out of 10 transact.  No error or any other indication that an issue with 2 lines encountered.  So, it is only after the fact that the missing 2 lines are discovered.  I have been unable to recreate the issue in any of our test systems so engaging Oracle tech support would be difficult...If I can't recreate it it is hard to try to fix it.  I'm looking