The bucks may have been shooting blanks since they have not been bred for so long.
I have heard of does mounting bucks because they want to be bred or it could be a dominance thing, how long did you leave the does in with the bucks on your second try?
Removing rabbits from a group and reintroduced them will stress them unfortunately.
How long did you leave the does in with the bucks?
When they are close to being due you should not move them unless you have to.