Crimson Shores map - head of the king ritual not turning on (also, wrong map objective?)

The Crimson Shores map has a boss with a delayed spawn.
For some reason after killing it the boss ritual (not normal ritual, specifically the one started with Head of the King) is unable to be started.
Also notably the map objective for some reason isn't killing the boss, but killing all the rares (which I'm pretty sure is no longer a correct objective).
In the end I was unable to find all the monsters, and thus unable to complete the map objective.
Bug report reference ID: 2960034548