Hi, thank you for your suggestion. I have tried it, but it doesn't work. I did figure out what was causing it just now.
Yesterday, I went back into the game and suddenly there was no problem anymore. No notifications, nothing. As I suspected, my work zone setup was correct all along, but the game was acting all buggy. I was in the game a moment ago. I decided I'm going to build a new habitat and the moment I've put the fence down (and nothing else at this point) and unpaused the game, the notifications suddenly start to pop up. The weird thing is, it only pops up for the jaguar habitat. Again, I haven't changed a thing in my work zone setup. So it's apparent that what prompts the game to consider my assigned staff can't reach the jaguar's habitat is a placement of a new habitat.