First record of stage write is always getting missed

Summary:

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I am passing a json as input to my app driven integration.

Input [{"name":"ABC","PersonNo":"123"},{"name":"DEF","PersonNo":"456"},{"name":"GHI","PersonNo":"789"}]

I am iterating each record of JSON and writing it into a stage write csv file and im sending that csv file as mail notification. Whenever I run the integration, I can see the first record processed and written to stage write in the logs, but in the file sent in the mail notification, I can only see last two records.

Always the first record is missing in the file sent in mail, but i can see it getting processed and written in stage write as per logs.