They both override the AnimalJobGiver and use their own....
Neither version of PAC makes any changes to AnimalJobGiver, but if the modified version of the method references something that PAC *does* change, that could potentially be the source of trouble. So I have at least an idea of where to look, now, when I get home. 
I guess you do the same for the pawns, and if your pawn jobgiver calls the original one or your own, it gives an error
because it can't find anything.
So the game has to wait until the jobgiver of the minions calls on them.
Other possibilities : Slaves are based on humanbodies, but I guess have a radically altered prisoner behavior in comparison
Minions are also based on the humanlike body .. maybe they get called because of this .. else other modded animals should create a similiar error. .. or not ..
Thirites Baby's on the other hand follow normal Pawn behavior and do work perfectly fine with PaC
----- EDIT -----
-> If someone could try the GameOfThrone Slaves .. they should show the same behavior as minions.
I just noticed I mixed those up with SlaveLabor from Thirite which forces Prisoners to work for you ..
RimSlaves/Minions are exactly the same. The same author the same main technique.