if there is something wrong when play back on monitor, such as freezing, video jump, try troubleshooting methods as below.
1. check if playback on all channels have the same issue.
2. check if placyback on all recording of this channel have the same issue.
3. format hard disk drive to erase everything in hard disk drive. record and check play back again.
4. restore system to factory default.(it won't delete video in hard drive)
5. send email to email@example.com with your system's model number where you can find it at the bottom of recorder to ask new firmware version to upgrade system.