Bees seem to be losing there home/wandering off in somewhat random directions. I've noticed that this can happen sometimes immediately after leaving beehives, pollinating a flower or some time in-between. It tends to be most noticeable when it starts to rain or become night as bees will continue to fly about. I've found bees that have wandered 50+ blocks away and brought them back using a flower in hand were they will usually repick a nest with room and go into it or try to fly off again (I have 6 hives and about 12 bees).