Quickbooks 2020 Mac Desktop.
Quickfill transactions turned on under Preferences/Data Entry.
If an entry is made dated 12/20/19 for a vendor "City of Wilmington" and saved, when the next entry is made with "City of Wilmington" selected, the fields will auto populate with the 12/20/19 data. So far so good.
However, if this new entry is then saved with a date of say 11/30/19, and another entry is made with "City of Wilmington" selected, the data that auto populates is from the 12/20/19 entry, not the last entry made dated 11/30/19.
So the software selects the most 'recent' entry by transaction date closest to today, not the most recent entry by the date and time it was actually entered/created.
This is a problem if you're entering a bunch of transactions from weeks ago and there is one transaction entered for that vendor with a more recent date.
The workaround, if there are a bunch of transactions to enter for the same vendor, is to save one with today's date, enter all of them then adjust the date for the first transaction in the series to the correct earlier date.
Just got off the phone with support and they were able to duplicate my findings.