u/Livluvcats

We got out LR5pro mmmm 3 weeks ago I believe. I’ve seen all three of my cats utilizing it. However I’ve caught my 1 cat pooping on our livingroom rug a total of 3 times now. I’m not sure what to do 😭 she uses it both pee and poop but for some reason decides what seems like randomly to take advantage of my rug. We had their old litter box out for 2 weeks but felt like they were using the new one enough to take the old one away. Previously none of my cats have had accidents. Anyone else experienced this? Pic of the guilty party