Error in invocations of troops

I wanted to see if you could check my account on the subject of the invocations of troops, I say that every time I summon the troop of dark reanimated fighters of 3 * … and I do not think that is very likely … because I always get that and very rarely the devout sacred warriors of 3 * … I think there must be some problem or bug in that sense and I would like it to be checked … Thanks