There seems to be a problem with the program "JustKaraoke" for Windows where importing songs into the database requires deleting and reinstalling the software to recognize the new songs, which also results in the deletion of saved singers. The question also asks about the cause of singer history not saving singers. Unfortunately, without further information, it is difficult to determine the exact cause of these issues. It is recommended to reach out to the software's customer support or the developer for assistance in resolving the problem.