Hi Kyung,
You might want to start by following the TN below to troubleshoot the FileReader restart:
https://support.symantec.com/en_US/article.TECH220459.html
If that doesn't help, then read the forum queries below:
https://www.symantec.com/connect/forums/filereader-constantly-restarting
https://www.symantec.com/connect/forums/dlp-v115-endpoint-agent-server-filereader-restarts-excessively
Thanks!