Automatic Litterbox Central

Hi,

I have a big problem. I have 7 cats and most of them are using the PSC quite well. But somehow or rather, I think 1 of them has been PEEING and POOING outside of it all the time. Can someone tell me how to resolve my big headache?

Otherwise, I must say the PSC is fantastic.

Please help me out... thanks. Otherwise, I need to spend time cleaning EVERYDAY, which is something i don't want when i bought the PSC.