Issue in Customer Balances FD33

Dear Gurus,

My client using fd33 transaction to see the customer balances, most of the time it is not updated keeping in fact that sales order are there, so it showing the wrong results, when after running the following reports "RVKRED77" data in fd33 get corrected.

can any of my guru share me that why system behaving like this, majority of the time it is not possible to run this report for every or all the customer.

Looking for the gurus feedback.

regards,