Whenever the DVR reboots an entry is created in the Log, Information>Log. In the log the entry will list "Reboot with flags" or "Reboot Symbol". It will show a code telling you why the camera rebooted. Please see the list below:

Boot Codes
0x00: DVR has rebooted normally: routine maintenance reboot or a user reboot.
0x01: Abnormal reboot: power loss, system crash, or other undefined abnormality.
0x02: Log stuck.
0x03: Hard drive read-write slow: hard drive read-write speed has dropped significantly; hard drive capacity has seriously decreased.
0x04: Abnormal recording: Over 3 minutes with no stream on the recording channel.
0x05: Bad track: The hard drive has a bad track.
Troubleshooting the codes
0x00: Check in Settings>System>Auto Maintain to ensure that the DVR is not set to reboot.
0x01: This one is the hardest one to diagnose. We recommend updating the firmware to the most Recent version, hard resetting the DVR, and ensuring the DVR is receiving consistent power.
0x02: Clear the log. Go to Information>Log and click Clear.
0x03: Check in Settings>Storage>HDD Manage and look at the Status. If it is not "Normal", it is likely that there is a hard drive error and it needs to be replaced.
0x04: Check all of the camera connections and ensure they are powered correctly.
0x05: Check in Settings>Storage>HDD Manage and look at the Status. If it is not "Normal", it is likely that there is a hard drive error and it needs to be replaced.