Oddly, as I've been trying to work this out I've run into other weird issues. I tried loading the level in game, and one of my test hatches starts out completely revealed, usable and everything, but when I use it the hatch goes invisible and I can't reveal it no matter what I set my wits to. My other hatch starts visible but unusable until I get close enough and the perception check kicks in, at which point it becomes usable.
At this point I think I've just broken these hatches, so I'm going to try starting from scratch.