Ah, the company and the cats will do that to a bossy stinker of a bunny! Hopefully he will be getting better soon. I’m somewhat in the same boat, and I too find that the xpen works well when having to do refresher courses.
Lately, my two have been seriously misbehaving in that department because our cat dared to peek into their area and dared to share their play area in the living room (they are still not fully accepting of the cat). Well, now it’s poop bomb central. Usually they taper off after they feel they’ve made their point, but it’s getting ridiculous and I think that true bad habits now are settling in since they are piling their poops instead of just territorial marking. I’ve tried some basic things like moving the litterboxes, temporarliy blocking the poo battleground, and that seems to help. But if they continue, I’ll bring in the big guns – the xpen. Usually, that always nips it in the bud, but I use it as a last resort since I hate to restrict their freedom since they are completely free range. Usually a week is all they need to completely get back to normal. We’ll see.
Keep us updated on your situation.