Is the manager a variable? Or is it always the same person? My favorite Nintex action is the State Machine. Have you tried using that? Start the SM with the approval, depending on the outcome, you can move the state to a different path, If approve, end the SM and end the workflow. If the item is rejected, have it move to a new path, give the clerks a task, in the task form, add a field for the manager they wish to send the task back to and set that variable to the same variable used in the original approval. Once they complete changes, have the SM change it's path back to the original start of the SM. It will use the same approval task and now send to the manager variable that the clerk changed it to. The cycle continues until the manager approves it. Does this help? Let me know if you have any questions

Thank you Chadd for your response,much appreciated. Yes i am using the State Machine for the approval and rejection of the item and both the Approval and Rejection work 100%, i have no issues. The issue is when the item has been approved and declared as a record and the user goes and modifies the properties of the the declared item(by undeclaring the item manually then modify the properties of the item). After modifying the properties and checkin the item, the workflow need to send an email notification with an option to to select the manager who will approve the changes.  This email notififcation needs to be sent to  the person who modified the item so that he/she can forward/route it to the manager to approve the changes.

About the manager, it is a SharePoint group with names in it