If you use bleach be sure to rinse really well!
I agreee with SQ that the more you clean them the harder they have to work at scentmarking their space.
What are you using for bedding? Is it deep enough? I use newpaper sheets, no problem until a kid shreds thu to the plastic cage bottom, pee sitting on something unabsorbant smells really bad really fast. Are your kids maybe moving the litter away in one spot?
As Arkeld says often the smell is not coming from the places you clean, but the places you don't. The odd rattie can and does turn their butt to the bars and spray it out, it can be on the wall or the floor or on the back of a stand. My worst smell problem was when I made levels for a cage and covered them with thick plastic, the pee had plenty of places to hide. I wash the cages in my tub with a sprayer on a hose, but pee gets anywhere and without dismantling the cage any one part against another will create a microscopic space where pee can be and even a powerwash might miss. So if you have removable levels be sure to remove them and clean all parts separately. And outside of the cage - check the walls & the flooring and the cage stand....