Hi Donny,
first of all, I suggest you to run the report TPM20 and select both options 'Posted business transactions' and 'Reversed business transactions' in order to verify what actual FI posting exist in your system at the moment - there is a column 'PostStatus', which actually tells you the status of FI posting. also, using 'Change layout' you should be able to add both columns '(FI) Duvoment (number)' and 'Reference Key'.
the only reason for the flow to be posted, though without link to FI document, that it was fixed with transaction TBB1_LC - Legacy data migration, when these flows are not relevant for posting due to the reason, that they were part of Legacy transfer over the Initial balance.
hope this makes sense.
Kind regards,
Renatas