Hi!
It’s great that you’ve been prebonding, that’s a really important step.
Is your hallway neutral? It could be that the space just isn’t neutral enough.
Was any skin broken? If it was, you need to take another break. If not…
Since you know they are likely to fight, I suggest you being much more involved. When I was bonding my buns, I knew that my female bunny has a tendency towards viciousness! So I spent the whole first week of bonding sessions with my hand on her head, petting her and reassuring her. If the boys came close, I would put my other hand between their faces so they didn’t have a chance to bite. After a week of this, I was more confident that she wouldn’t immediately start a fight with them, so I backed of a bit, but still had my hand hovering over their faces during any interactions.
You could also try the smooshing method, where you just squish them next to each other, pet them then separate. This gets them used to being in close proximity with positive feelings, but they can’t fight.
You need to identify what causes the fights (eg – girl doesn’t like boy sniffing her bum) and then prevent that behaviour, at least until they’re less jumpy with each other.
You could also try increasing or decreasing the space they’re in, depending on what causes the fights.
If the vacuum works well, then it may be that stressing them would work, so take them for a car ride.
Basically, there are many options, and no one way of bonding works for everyone 