Certain raids in the game are scripted and thus guaranteed to occur a set period after claiming the settlement they occur at. Gunners at Finch Farm, Super Mutants at Abernathy... those not governed by the regular raid system.


These raids just pop a 'Help defend..." objective in your miscellaneous quests without any indication, whereas regular random raids present an unmissable dialog box telling you a raid is taking place. These should be clearer - only noticing them while casually paging through the Pip Boy means these could unfairly time out and fail before the player even knows what's going on.