They keep ****ing on the back inside.

Last time, instead of wiping, I just sprayed (not me, I mean with a
spray cleaner) the backside. Since then, looks like they have been
peeing down into the litter instead of on the backside. Doing okay
now. The way to tell is by using a flashlight. When tilting the
litter back into place, quite a bit of dust is generated as it moves
back out of the filter area, but most of that dust stays inside of
the box. Anyways... That will be it unless there are any more
questions.