I don't think the rabbits 'fell out' because of anything relating to them, or their relationship. They fell out due to an error you made (don't worry, we all make them, we just have to learn from them) of increasing their space too much, too soon.
Having too much space, too soon encourages the running, chasing, circling and then fighting that we always try to sidestep by using a small space, as a general rule, for bonding.
They exhibited, to be honest, the behaviour one would expect to see in that situation, and if you hadn't, you would have been very lucky.
If you want to try again, maybe go right back to basics and start from scratch, moving far slower and following the rules closer.