Did this happen as soon as you removed the other cage or has it progressed to this? Only 20% use is a pretty significant change. I would think about a vet check up to rule out health issue causing this. Do you have a similar type surface as her cage floor was in the new pen area? Maybe that will help it feel more like her former cage.

I think it could be a couple different reasons. At about a month, a bunny stops feeling “new” to your home, and may decide to “claim” it as hers. This could be territorial marking that she is doing all around the cage because she is so happy to have a new home that she wants to make sure that no other bunny comes along and steals it The problem with territorial marking is that once a bunny does that all around the cage, sometimes they then realize that the whole cage smells like a litterbox and they continue to poop outside the litterbox. So in our house, when a bun is pooping or peeing outside the cage, we have to go neat freak on them, and clean the cage as often as we can, anytime we walk by the cage we throw and poops left around into the litterbox, and clean up any pee with vinegar, in addition we shop vac once a day. One way to make this a bit easier is if you have left over old sheets, you can put one down to cover the floor and then replace it each day with another, and shake the old sheet out and wash it and the switch it out the next day. Regardless, I think the most important thing is to keep the floor of the cage as clean as possible.

If the marking outside the box is just in one place, then that could just be the place she has selected for her other litterbox, and I would put another litterbox in that area.

Did you try putting another litter box in the area she has decided to use as a potty instead of her usual box? I know when I moved my monkey to a new room, i had to put another box out for a bit until she got used to the new area.

I didn’t mean to worry you. I don’t think there’s a need to bring the appt forward – just bring it up at the appt you have. It does sound due to the cage change judging from the timing. Health concerns are something to be on watch for when there’s a loss of litter habits but in her case it does sound behavioural. Good you happen to have an appt all the same. I would try some flooring like vinyl or plastic sheeting. Maybe you cleaned the litter box too thoroughly for the transistion. Mop up urine with paper towel and poops and put it all in her box. What you are doing now, keeping her space small is good. She should regain her habits in not too long. Fingers crossed!