Automatic Light

This is a story from my workplace. I work the night shift at a serviced elderly housing facility, and I wait in the common hall. There's a shared restroom there, and it has a mechanism where the lights turn on when it detects movement. But the lights suddenly turn on in the middle of the night when no one should be awake. When I asked colleagues who worked on other days, they said the lights turn on once or twice in the middle of the night too.