Unable to import data using OOB excel import export

I am trying to update and insert data in one of my custom entity using oob export and import. However while doing so, it fails if we use excel as source format, because rowchecksum keeps changing. And .CSV format fails for update and succeeds for insert.
This error is received while trying to update records using .csv file. 
And .xlsx file error is because of Rowchecksum this error is received-