Do you allow date/period mismatch? If so, this is your issue.
Financial reports, like the balance sheet and trial balance, are based on the posting period. The aging reports, by default, are based on the transaction date.
Check accounting preferences you can change Aging reports to be based off transaction date or due date
If you allow a date/period mismatch, you'll have variances.
And The standard AP aging report includes ALL accounts of account type "Accounts Payable”
Add a filter to filter for only the AP account that matches to the B/S account you want to see
If anything change you need to trace the earliest period with discrepancy and manually trace the discrepancy per entity.