I have a protected run, hadn't lost a chicken to a predator in over 2 years.
The young ones go to bed alot later than I often do. My run is covered by 1x2 welded wired. One night a couple of weeks ago, it was warm, I had to be at work at 4:30 am, and I figured they would be ok.
I didn't think. Instead of going inside at night, they were taking to roosting on top of the pop door, about 8 inches below the wire. I lost one that night, something reached in and pulled it out. There noise and peeping woke hubby up, otherwise I probably would've lost more.
We corrected the problem, they go in at night, no matter what, and we put up a piece of plywood above that pop door.
We put a piece of plywood up on the side of the run also, looked liked a bad situation, but I have a roost going across there, and we have a feral cat hanging around, and I noticed today that I have one chick who likes that roost, and leans against the fence, so the roost is coming down tomorrow.
I don't have a problem in my other coop/run with my older chickens. Setup is the same, but a 6 ft high run, rather than a 5ft run, and the all go in at night, even with the coop doors open.
Before you leave them out, just look at all of the options of a predator.
I'm getting old and get up several times during the night. Since this happened, if I go to bed before they do, I set my alarm for just before dark, I figure I'll need a break, then I go out and make sure they are in.