If we suspect something is wrong with the DVR unit, what diagnostic steps should we take to eliminate other problems aside from the obvious ones of using the reset button on the unit, reinstalling the firmware, reformatting the memory card and/or testing the memory card with a memtest program?
You can also use an external power supply (output 2.1a or greater) to connect to the DVR, which requires A lens to connect to the DVR.
Then you can see if the DVR works with external power.
Also you can switch the front and rear lenses, and then power up again to check whether the lens is working properly.