I've asked this before, but would you know why my cat sometimes poops on top of the litter box lid (top entry) instead of doing his business inside? Nothing has changed. It gets cleaned the same, the litter brand is the same, the location is the same, he's not sick. I swapped his main litter box with the secondary box and he was using that just fine for a few days, but then this morning he decided to poop on top of that lid too! And then later when I happened to be right in front of it, I watched him go inside the litter box no problem.