There are a whole range of reasons. If it rained recently, or will rain soon, or if there are thunder storms in the area, or it's too early or too late in the day, or you squished a couple of bees, or they don't like the smoker fuel, or there's a dearth, or the planets are not aligned harmoniously

Bees are considered hot if they are bouncing off of you just for approaching the hive. If they stay mean through several inspections, then you need different genetics (again). Even Apiaries known for very gentle queens will produce a hot one once in a while.
As for drone brood, they want to have 10 to 15 % drones naturally. We don't really let them do that by supplying worker size foundation. If you pop some foundationless frames in there they will draw the first couple entirely drone size.