It could be worth a few stress sessions to really cement things in place. Are they both fixed?

I know this is your third or fourth post about them, and as I said initially it seems like it was pretty rushed. Especially if you keep having issues. You might want to go back to basics and slowly bond them over the course of a weeks, not just days. It sounds like they really never worked on their hierarchy during initial sessions.

If they bonded ‘very easily’, perhaps they didn’t properly sort out all issues during the bonding process.

As A&B says, you’ve posted a few times about them having problems with their bond, so they might not even be bonded. It sounds like the male is very tolerant, so where another bunny might cause fights (which would make it easy to say they’re not bonded), he’s just ignoring it. That said, it’s not fair to have one bunny be constantly bullied by their partner. Although occasionally there is mounting in bonded pairs, it shouldn’t be a regular occurence, and nor should chasing. Normally we would declare bunnies bonded when there’s not only positive behaviour, but also no negative behaviour, so they’re not really meeting that criteria.

I would go back to basics and do some bonding sessions in a neutral space where you intervene every time the female behaves in a negative way.

Unfortunately there’s many things that upset bunnies’ bonds. I had to separate mine recently after a vet trip (that they all went on together) when my female decided to start bullying the males. Moving house, a new pet, more space, less space, even just spring have all been known to upset bonds. Happily, rebonding my bunnies was much quicker the second time round, but I do think some bonding sessions would do them good.

Newly established bonds can be very rocky to variables we can’t even perceive. While the time line isn’t as long as 6 months, I know my local rescue recently bonded two rabbits with each other. It was a seemingly very strong bond, supervised for over a week. When the family came to pick up the bonded bunnies though, one immediately started, non-stop humping the other. We have no idea why– a fragrance a family member was wearing, the rabbit was trying to show off in front of new animals…. but once the family left, the humping immediately stopped and they were completely fine. Rabbit bonds can be very solid, but in those beginning stages, there are things like scent and interactions between them that we aren’t attune to which may upset them or drive the need to reassert dominance.

It could be you’ll never be able to find a reason why, but what’s important is you’ve noticed this new, distressing behavior in the bond, so going back to basics or revisiting some bonding sessions may help the rabbits resolve it between themselves.