You said that integrity checks were run. Were they clean, or were errors found?
Yes, they were clean, no errors found.
Have you ever had to get data rebuilt or fixed due to any previous posting errors in GL?
We had a duplicate posting issue around the same time, but this occurred from GL to Bank Rec.

I will compare the difference in subledger to general ledger balance last month to this month. If the 'triple' posting of this matches the variance, the correcting entry is clear.

Thanks,

Lisa