Payment Groups A/P

Hi ,

Can anybody explain to me what happens behind the scene wen you click on 'Update' , for an A/P Payment group . The reason I want to know is that we have payment groups that do not clear during the update part of the run , they are left behind on the F04572 file only , this causes a problem when the payment number rests itself and tries to put new records into an existing payment group from a few weeks earlier.

Would really like to know why it doesn't cler for some accounts and others are fine.

Thanks for ll of your continued help