When was her last vet visit?

Any change in behavior is a cause for concern. Especially in an older bun. Peeing outside the box can be a sign of a UTI or bladder problem.

It does sound like she has had some trouble from UTI in the past. Is she dribbling or do you see her consciously left her tail and go?

How agile is she? How do her hocks look? It might be worth trialing a lower litterbox and/or softer litter in case she has aversion to the box for some reason.

Thanks for the update. I hope you see some improvement with this treatment.

For many years, Jersey had litter habits like this. She also drank a lot and had very dilute pee at times. It was difficult to tell if it was behavioural or medical with her. In hindsight, I think it was a combination. 

Is your girl with another rabbit?  I seem to recall you had a bonded female pair. Very likely I’m mistaken! 

We had a member post recently whose rabbit was getting a wet tail on and off, mostly she stayed wet. She was on various antibiotics. They’d see improvement but then a relapse. They thought she might be reinfecting herself and found that regularly wiping the soiled area helped. They used alcohol wipes. There are probably alternatives you could use or a solution you could make up yourself using something like chlorhexidine. There are also baby wipes called Water Wipes that have grapefruit seed extract in them. It’s a natural anti-bacterial, anti-fungal. Another member mentioned they got these from Target.

Best of luck! Hope this takes care of the problem.