ODK Briefcase duplicates records IF Export repeated with previously-exported CSV present

What is the problem? Please be detailed.
Briefcase seems to append and duplicate records IF Export is repeated WITH a previously-exported CSV already present.

What ODK tool and version are you using? And on what device and operating system version?
Briefcase 1.8.0 (also1.4.9 and 1.6) on Win

What steps can we take to reproduce the problem?
Export. Inspect the CSV
Export again. Inspect the CSV. The exported CSV will now contain double the number of records.

What you have you tried to fix the problem?
Move exported CSV's to a separate work folder. If Exports are later re-done for any reason there is no file to be appended to.

Anything else we should know or have? If you have a test form or screenshots or logs, attach here.
This happens only if a previously-exported CSV is present. It's a minor issue. Small teams handling several, large, oft updated datasets may be at risk of occasionally producing end products with duplicate records.

When you are again exporting CSV file then you should use Briefcase and you need to overright this function is already available in ODK Briefcase.

Please go through with below link and your concept will be clear like a crystal.
Go through with Command Line Interface, this is one of the best tool for exporting software.