Not sure if it’s a bug..
When I want to clear the outbreaks, I go to each zone and if there isn’t an outbreak, I make one (burning 3x embers + effigy).
Granted, I’m end game with hundreds of each resource.. so for areas like the Nameless Pass, Woods and Meadow, I always use the effigy so I’m not spending a bunch of time running around when all I really want is the boss loot.
If you’d like to learn more about the outbreaks and how their scaling difficulty does not affect non-boss drops: