We use the CsvUrlImport to fetch monthly billing data.
Ignore Duplicate Timestamps, Ignore Duplicate Records are all set to TRUE.
COV is set to TRUE.
If we run the poller consecutive times with the same import data, the very last record is duplicated for each time it runs.
This may be a bug in the Niagara history database, but I would expect the above setting would prevent this.
Interestingly, if we attempt to edit the history and set the duplicate records to zero, the editor only allows us to update the last record.