I had this same problem after one of my buns was neutered and lost all his litter box habits. We got to the point where he would really get flustered (as would we) and we had quite some tempers raging in the house. My boy, Fleury, also started getting very aggressive whenever he’d have to pee and we’d notice.
I used just about every trick in the book to get my bun to go and of course, he kept going on the carpet. I completely understand your frustration. I actually used clicker training to teach him he gets rewarded for going in the litter box. I’m not sure if you’ve ever looked into clicker training but it’s really simple and after about a week my boy caught on and has only had a few accidents over the past 3-4 months.
To begin — he’d get a click and a treat for stepping IN the litterbox. Sometimes I’d give him a little nudge on the rump in the beginning since he didn’t understand me obviously. Fully inside, not just reaching in. I could eventually say “Fleury, Litter!” and he’d hop in and turn around for a treat. Then I started paying attention (taking a few hours out of my day) to watch and see when he’d get ready to pee (tail up, hunched over position) and I’d quickly say “Fleury, Litter!” Knowing that he was about to get his favorite treat, he’d jump in and I’d keep him there until he peed. After a few times of peeing and THEN getting the treat he began to figure it out. Every so often we give him a treat when he’s going in the litter box to help keep up the good habit. I would try and see if this helps you out!
If you have any questions about clicker training, you can ask me! I’d be happy to help.
Also, are you making sure to clean up all the areas so no scent is left? Say with vinegar? Easiest and cheapest solution.
I also was forced to minimize the space ALL three of my buns occupied to get him back to being almost perfect. Instead of having the whole room, they were kept in a smaller area until he got the hang of the litter box, then I slowly made the area bigger and bigger until there were no more accidents. If he had more accidents in the bigger spot then it was back to the small spot for a few days. I understand that some people don’t feel comfortable not giving their buns the option to roam for a few days though so I understand if thats not the way you’d like to go. We were eventually forced into doing it because as my one bun lost his litter habits, the others began to follow suit and decided to pee all over also. Oy vey!