I have received the below message when I tried to upload a Batch:

Database.Error[getFields=();getMessage=rC_Bios.Contact_AfterUpdate: execution of AfterUpdate caused by: System.ListException: Before Insert or Upsert list must not have two identically equal elements (rC_Bios) ;getStatusCode=CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY;]): method = updateContact

What is the best way to resolve this error message?

Thank you!