DVR time reset while working

Hi every one. I came across a no name DVR that the time add date reverts to the default date and time while working you can see when it happens after the correct one was set.

Has any one come across this problem before? what could be the cause of it?

I would open it, look up if there is battery on the motherboard, and replace it with a new one. Worth giving it a try.

I am going to try that. That normally happens when the system looses power, but I actually see the time change back to default. Like in 8 to 10 seconds .