File Reader will restart because it has not received a heartbeat within the timeout period. Increasing it can reduce the number of File Reader restarts.
15.x
1. Enter the advanced settings of the server in question.
2. Locate and increase value the following Advanced Server Settings: BoxMonitor.HeartbeatGapBeforeRestart
The heartbeat is expressed in milliseconds.
3. Save changes and recycle the server.
See also: Article ID: 16014 DLP File Reader restarts excessively