Hi, I have 4 outdoor cats. One of them however does not venture out of our back garden. The 3 other cats all go to the toilet outside but we need to keep the litter tray as this one won't. She does use the litter tray, although every morning we wake up to find that she has done it in the hallway. It's the same every morning. She does it not long before we get up but for the rest of the day she will use the litter tray. Do you have any ideas on why she might be doing this and how we can prevent it? We don't know what to do as she already knows to use the litter tray. We don't think it has anything to do with the cleanliness of the litter or when the litter is changed.