1) a lot of late afternoon activity can be orientation flights. That is when the younger bees are taking their first flights outside the hive and trying to orient themselves to the hive's position visa vi the sun and what the hive's distinguishing marks may look like, ect.
2) as far as a lot of drones later in the afternoon, that is the time they tend to come back from the DCAs (drone congregation areas) where they have been waiting a good part of the day trying to catch a virgin queen on the wing. By 4-5 p.m. most virgins queens have already done their mating flight thing for the day, so the drones head back to the hive to grab a beer and call it a day.