Replacement fees are always removed from the patron's account if the item is returned and have not yet paid the fee. The processing fee is removed if the policy has been configured to cancel the fee once the item is returned and the patron has not yet paid the fee.
This setting can be found in OCLC Service Configuration, open the WMS Circulation from the left menu, select Loans, and then select the Long Overdue Policy link. Within each policy listed there is a checkbox to Cancel Processing Charge when Item is returned.