a problem with a VCR's clock

i have a panasonic NV-SD235 VCR. when i unplug it from the socket and then replug it the clock is reset to 0:00

i know that this shouldnt happen. the VCR should have a backup battery which it claims to have. so whats the matter.

and i havent contacted panasonic about this

Could it be that there is no battery and your VCR uses
capacitor just to bridge short power interruptions?

Assuming it's an old video, it may have a backup battery (but it's almost unknown on any recent ones) - the batteries though, particularly the rechargeable NICAD ones, are very prone to failure.