I saved my zoo, closed the game, and restarted it. Hardly anyone getting stuck now. I suspect this is a memory leak. I had the game open all day when I posted this earlier and the people getting stuck just got worse and worse.
I've run into this a few times too. I've had zoos where restarting didn't even help, and I basically had to abandon because something unworkable kept happening. I had one where animals were constantly escaping by just walking through barriers, or where the game thought they were escaped when they weren't. I also had one where I had a couple of habitats that staff could not enter sometimes, even though there was nothing wrong with the gate or path leading up to it, nor with the traversable terrain inside the entrance.
But for some reason, starting a new zoo that is basically the same layout doesn't produce the same issue.
The weirdest was the one where a vet got perpetually stuck, grumbling and groaning, outside a habitat trying to remove a dead animal. It got even weirder, because guests kept behaving as if the dead animal (which could not be removed from the habitat) was escaped. A recent update seemed to fix that problem, though (I sent Frontier the file for that zoo, so maybe it helped them figure out what the issue was).
The curbs/kerbs and ribbons can work to direct guests away from problem areas or to keep them moving in one orientation or vector through an area. They don't work for staff, though.
