The European wild rabbit is a social animal in its wild state. They live underground in warrens, which are groups of burrows of many individual rabbits. For the domestic rabbit, the rabbitry has become their warren. They feel save and secure in their cage, which has taken the place of the burrow and become their home. The does are more protective of their cages that the bucks.
Nature makes the does that way to protect the young from intruders.
Putting a buck in a doe's cage is never a good idea. If you are going to breed the rabbits always take the doe to the buck's cage. The buck will certainly make her feel welcome. You should not keep moving your rabbits from one cage to another in your rabbitry. Give your rabbit a permanent cage, especially your does.