mule 4 sftp file read is deleting file after file read - mule

Question

Using Mule 4.4 community edition .
I am reading a file using mule's sftp connector :
<dependency>
<groupId>org.mule.connectors</groupId>
<artifactId>mule-sftp-connector</artifactId>
<version>1.4.1</version>
<classifier>mule-plugin</classifier>
</dependency>
Running code in dedug mode , after the file is read , I can still see the file on sftp location ( which is good ) , however it disappears after file read .... ( see below code )
<sftp:config name="SFTP_Config" doc:name="SFTP Config"
timeBetweenSizeCheck="30" timeBetweenSizeCheckUnit="SECONDS">
<sftp:connection host="myHost" port="22" username="myUser" password="myPassword" />
</sftp:config>
<until-successful maxRetries="1" doc:name="Until Successful" millisBetweenRetries="30000">
<sftp:read doc:name="Read employee file" config-ref="SFTP_Config" path="${sftp.inputDir}\employee.unl" timeBetweenSizeCheck="-1" outputMimeType="application/csv; streaming=true; header=false; separator=|" outputEncoding="UTF-8">
<non-repeatable-stream />
</sftp:read>
</until-successful>
<choice doc:name="is the file empty ?" >
<when expression="sizeOf(payload) == 0">
<raise-error doc:name="Raise error on empty file " type="FILE_NOT_PRESENT_OR_EMPTY" description="Employee File empty "/>
</when>
<otherwise >
<logger level="INFO" doc:name="Payload not empty" message=" #[sizeOf(payload)]" category="employee"/>
</otherwise>
</choice>
So when the code enters the choice condition I can see the file is somehow no longer available on SFTP drive ...
I have tested this code in debug mode to verify when the file is getting deleted / disappearing.
Not sure why this would happen ?
why is the file getting deleted after code enters into the choice condition ?