How to restrict creation of new warranty when we ship back repaired item in case of loaner scenario?

Summary:

Customer has a loaner program where they offer a loaner item in replacement of the defective item till that time is under repair.The loaner item is company's asset and not customer's asset. When the repaired product is shipped back to the customer it should not create new warranty and it should re initiate the original warranty. Also, the install base is receiving "create operation" instead of "reinistate operation" in re"reprocess installed base updates" when the repaired item is shipped back to the customer. How can this be achieved?

Note : We are not using service logistics instead we are using third party service max (SFDC).