1. In Records, Clients, open affected Client record
2. Select the Activity tab and open the appropriate invoice
3. Select the Line Items tab and open the appropriate line item
4. Select the Payments/Credits tab
5. Highlight the second  row listed under Responsible for Payment and click Delete
6. Click the black drop-down arrow next to Add/Edit Applications and select "Unapply All and Distribute Evenly to Current Payers" and it will unapply the payment
7. You can proceed with applying the payment to your correct invoice