Get auditors who understand QB, or stop them from any jounal entries. Journal entries should be the exception when using QB, they often do not work as you think they should, and when you use inventory type items they never work for inventory. It is much better to use the forms on the home page the way QB is designed to be used. Journal entries also bypass accrual/cash reporting, and will not show on many reports.
You said a payment was made at the end of the fiscal year to the previous fiscal year?
so a 2019 payment was backdated to 2018? not kosher at all.
The date the payments is made, is the date it gets recorded on. Even if you paid a dec 2019 bill in jan 2020, the payment date is jan 2020. in accrual based reporting the date of the bill sets the expense, and in cash basis the date it is paid sets the expense - that is normal accounting procedure.
you need to find out why they did that, and delete the journal entry they made, then if the reason makes sense (and so far it does not) make the entry correctly in QB