You say it happens around the same time of night, why not huddle in the same room again but this time set up your mobiles on video call. A couple of you leave your phones in the hallway and at the entrance, then securely sit in one bedroom and watch on the other mobiles or even better, on a laptop / PC. Be sure to record everything.

Webcams and Wi-Fi cams are really cheap so that would be a better option.

But if I were in your position then I would face it head on, there is a group of you against this one thing. It’s better to be the predator rather than the prey.