Automatic Litterbox Central

Hi, everybody, I'm Michaelle from washington dc & glad to be joining the group.

I have 2 middle-age mixed breed cats, who live w/me in my 7th floor condo. Both have used the litter robot for years. About 3 or 4 mos ago, I got one og the new larger globes. Both cats were using it w/no probs. The the larger cat would go in to peep, but poop on floor right ouside of the box. She will go inside, pee, cover it w/litter & come on out. No idea why. I empty box, wipe insde top & wondow w/baby wipes, bought the (outrageosly priced corrugated cardboars ramp form company. I washed the carpet yesterday & put on carpet freshener. Maybe that will he;lp. She seems a little tiny bit unsteady on the ramp, but I dont know if that's significant. Any thoughts/ THANKS