We got a new Hikvision security system a few months ago and after setting it up I would do random checks every time someone would leave or enter the house to make sure that it was picking them up. On two different occasions I noticed that it did not record when someone entered the house. I thought ok this is weird but today after doing a random check I noticed that it did it again. What could be the reason for this? 99% percent of the time it works....