Patent duplicate payment

It seems that you are talking about the patent license fee. It depends on how you agreed when you signed the license agreement. If the license fee is agreed to be paid in one lump sum and can be used for many years at will, then you don't have to give the patent license fee to the current patentee. Because you have paid the license fee to the previous patentee, when the patentee transfers the patent, it transfers the defective patent. According to the principle of good faith, the assignor should prompt the assignee. If there is no hint, it is also between them, not you. If the license fee is paid once a year or in installments when the patent is licensed, you should continue to pay the license fee to the current patentee after the license expires this year.