I have upgraded 30-40 devices this series from different release date, failed with none. Some of my customers are failed with upgradeing, and i had to restore the devices with
TFTP. The firmware works.
Golden rules to make proper upgrade when avoiding failure:
Better is to have monitor connected to recorder - you see your progress more informatively
1) Before upgrade stop recording, even better disconnect hard drive. disconnect wired alarm inputs.
2) Reset to factory default. Reboot
3) Do the upgrade - give some time to do its business - 5 minutes even
4) When up and running again, factory default again, reboot
5) Feel free to make your setup