PLEG Occupancy script

I have an occupancy pleg that uses motion detectors, ping sensors and garage door sensors to determine if any one is home. It mostly works fine. There are times at night when my wife and I are going to sleep, and therefor wouldn’t be tripping any sensors, and my kids may be going out for the night. I am trying to create a condition that
would let me know if someones is home and most likely sleeping. I basically want to know if someone went up stairs and hasn’t came back down yet. I have a motion detector at the bottom of my stairs and at the top of my stairs. Here is what I have so far:
(FoyerMotion; UpStairsMotion < 00:00:15) and NightTime and Not (UpStairsMotion; FoyerMotion < 00:00:15)
Last night when we went to bed it turned true, but 2 minutes later it turned false. Any help to correct my logic would be greatly appreciated.

You should be able to find out why by looking at your STATUS report.

If you want others to help you need to publish your STATUS report.