Total comp statements Employee cost values not updated after import

1] Total comp statements is System form which is having Additional benefit line Item which is having validation on UI for employer cost refer attached screen shots.

When importing data Employee cost through import it is not showing on Total comp statements at employee level refer attached screen shots.

Cross verified on Stage it is updated successfully.
2]When importing Data for additional form import got failed below is error log:
ErrorID : 0
ErrorSource : ControllerAppTier.SaveAndGetData->WORKTERRAControllerAppTier.SaveAndGetData->ExecuteImportDTS.ImportData->ImportValidation.ImportData->ImportValidation.GetImportExportFieldsData
ErrorMessage: Conversion from type 'DBNull' to type 'String' is not valid.

tried on more than 2 company please check.