While this doesn't solve the issue, it may shed some light on to what is happening (or may not). I have a client that has a bunch of pizza hut restaurants. AP is processed as one division. But every once in a while, the controller likes to see an AP Aging by store. So we wrote and access/crystal report that pulls the data from AP Open invoice table and the AP Invoice HIstory tables. We use a GL segment in the AP Invoice History Detail file to determine the store number to develop the aging by store.
Long story short, this works as long as the client has not ADJUSTED any ap invoices. For some strange reason, MAS does not write the adjustment line to the AP Invoice History Detail table. So we advised the client to NEVER adjust an invoice, process a new invoice.
So to finish off this sad tale, I will bet this is the issue in your situation also.