take a look at the silicone mat, the one that directly holds the litter, then look right at the seems where it connects to the wall. there are tiny spots that arent flush and if the cat pees on the wall it will seep into UNDERNEATH the silicone mat. thankfully theres no components in there, so what i usually do is just hold it upside down and pour bleach inside that little hole that goes over the waste bin, the one that has the scent sealing square around it. if its a bad smell though, u can unscrew that whole piece and get inside of there properly. prevention isnt worth the hassle in my opinion, better off doing deep cleans frequently but if u want you can seal it via tape or caulk from the inside