Honestly sounds like my Wick, who understands my preference for the litterbox but acts against that pretty often. I have many pee spots on my carpet that I just dont attend to anymore because once it’s there, he usually doesn’t go over it again. Thus, I am resigned.
That being said, we have worked out a system of understanding that if I do catch him, there are steps we go through: either he dashes to a litter box or, I follow him and hold him in one until he pees. If he already peed, I put him in the box anyways to make a point. From this, the adherence is probably as good as it can get with him and I do think it got me past what was previously a plateau of a lot more peeing on carpet per day.
Having a sound helps since sound can be made immediately versus you moving to stop the rabbit takes time. I do a loud hiss sound whenever I catch his tail lift outside the box and now that has established whether he will immediately go to a box or tolerate me following him so he gets to one.
In terms of why he’s doing it, just remember that litterbox training is a very arbitrary concept to rabbits. The perception that they can be litterbox trained is taking advantage of their general habit to poop and pee while they eat and in secure corners. If we were to reduce it down, it’s us telling an animal “These are the places you must pee in… that’s it.” I think some rabbits just seek more freedom and enjoy peeing on soft things beyond that restraint we give them.
More litter boxes, especially near those areas so you can easily shoo him there, may help.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.