Field Mappings are not working for Robust Transform Maps

Hi All,

I am trying to configure Robust transform in SCCM Service graph connector. All records are getting inserted But individual fields of the records like last login user are not getting populated. 

For example: If delete a ci record and reprocess the import set , new ci record with all details is inserted.

if I deleted only one field and reprocess or run the robust transform again , the field is not getting updated why?