Hi, I encounter an issue when products are returned. All products we ship out are scanned on unique serial number. When a product is returned we verify this based on the serial number and then the product will be added to the stock. 

The issue I encounter is that when the product is added back to the stock, the product can not be added in a new order. When we fill in the SN I get an error notification that the serial number already exists in our database. 

What can I do so I can use this SN again?