Just make sure you never end a bonding session on a negative note (such as a fight) as the next time you put them back together again they are more likely to fight in that bonding session too as they will associate the other bunny with negativity. Obviously if you keep separating them and they immediately start having a very serious fight then that is different, however with just little fights you should just stop them and leave them together.
Try ending a bonding session with scattered pellets or herbs, both of them placed together between your legs (if possible) with you giving them head rubs or even just them ignoring each other is positive. Obviously them grooming each other or laying next to each other is also a good sign and a positive way to end a session but it doesn't sound like that would be possible yet. I do agree though that it is probably best to wait until they have all been spayed and their hormones have died down before attempting it again.
