second biliography list generated when I add some new references


I wrote a manuscript containing a bibliography list of the references cited in the text. I send it to my client for corrections. When the revised manuscript came back, I had to add some additional references. When doing so, the new references are added as normal in the text; however, a new bibliography list with these new references starting agin with number 1 was generated after the original bibliography (references 1-39). If i remove all references in the text and add them again, they are added then in the new bibliography list and the problem is solved. But it is a hudge amount of work to do. It is the 2nd time I have this issue on a manuscript coming back from a client.

Do you have any idea how to solve this without having to add the all references again?

Thank you very much!

Kind regards,