It is the last possibility, steam locomotives are basically evil and take great delight in humbling and embarassing the crew. Any time things are running smoothly and tempted to relax, it is time to watch out because you are just about to be bit in the rear.
With considerable grade or speed limit changes at all of the SVRy crossings, we end up whistling with one hand and adjusting throttle and train brakes with the other. All the time watching for people and auto traffic. Very high workload for a few moments, then back to steady running mainly monitoring the locomotive do it's thing.