I have a camera that will not hold its own time without a link to an NTP server of some sort. If I log into the camera webpage it automatically syncs the time to my computer but after that point it starts to drift until at some point it decides it's 1970.The camera turns on the White light OK, so I do not that the time is an issue,
So if your camera is doing the same thing, you're logging into the camera and the time is synching so it's correct and the white light comes on because the time is correct but then when it's time for the light to go off the time has drifted so it doesn't turn off then when you log back in suddenly the time's correct again.
It's worth investigating rather than simply ruling it out.