One Re-Bond Later and Still Fur Pulling!

Argh! A few months ago I noticed Roxy had started pulling Leo's fur out for no real reason. It wasn't particularly aggressive. If she was sitting behind him, she'd just pull out a piece of fur from his back. He'd move away and she didn't bother to follow. There was no lunging/ growling or anything. I guessed it was because she was just bored, as I'd recently gone back to college and wasn't around to amuse them. So I ended up changing the toys around a bit, making a few new ones etc to no avail. In the end I had to seperate them as Leo was almost completely bald on his lower back (No bleeding/ broken skin though). I did suspect mites or some type of parasite, but Roxy was unaffected and Leo's fur grew back after being seperated from her.
I kept them in seperate tiers of the hutch, and they had side by side runs all the time to avoid completely breaking the bond. They had a few 'dates' for about 10 mins at a time with supervision and they basically acted as though they had been together the whole time. No immediate fur pulling.
Since breaking up for Christmas, I have rebonded them. Apart from some humping from both parties, all was fine. I did notice Roxy pulled some fur from around Leo's neck/ upper back during this, and Leo was attempting to do the same but has no teeth so nothing happened.
All seemed fine for the first 5 days or so, Leo was a little bald around the upper back but I hoped when the humping died down it'd be fine. I've since seen little humping (only the 'normal' amount), but over the last few days Leo is going bald on his lower back again
If it continues they'll have to live seperately, which is a shame because they do seem to enjoy being together. They both groom each other and they sit together most of the time. If I have to seperate they'll always live side by side, but I'd much rather we could sort this problem.
As I said, it doesn't seem to be aggressive fur pulling, as there's no chasing or lunging. I think it's more a 'habit', which I was hoping to break by having them seperated for a while . Does anyone have any ideas of what I can do to stop this? Thanks :wave:

To me that screams one of two things, a, that she is a 'nurse bunny' and is aware of something going on inside and wants to 'make it better' so I would watch for any signs of illness from him, and b, a maladaptive behaviour on her part. These can be beaten, but probably only if he warned her off and told her it wasn't ok.

To be honest, I'm not sure how you could beat this if it is maladaptive but I have had other bunnies with odd behaviours who have managed to beat them and go on to have happy bondings.

Im not a 100% sure as I am not an expert, but my rabbit Jack has 'sticky bottom syndrome' and my other bun Lucy always trys to pull the poo of his bum, maybe she is trying to groom him but being abit more forceful about it. You could maybe try sitting with them for 20mins a day an stroke them both this will encourage them to groom and cuddle each other in a nice way an you could also try brushing him abit more, maybe she thinks his fur is untidy hahah but make sure you tell her off when she does it, it sounds silly but my rabbit Lucy jumps on the dinning table and as soon as you see her she runs off because she no's full well shes not allowed up there speak to her firmly and push her head to the floor because she might think in her mind shes helping him. Hope this helps