I’m not sure if I’ve just never noticed… but do undead not count towards corpse count? Specifically for Scarlet in duels. I had at least 10 minions die before I ever got a corpse. The minion that died and counted towards corpse count was, in fact, an undead, but am I missing something? Ik about the Paladin bug… are there other things bugged too? or am I just dumb? 
Not sure where the line is drawn either, but I know spent corpses that yield minions wont return to being corpses as they get killed. But minions spawned as a result of killing enemy minions (think the ice skeletons that deathrattle for 2 dmg to a random enemy) will yield corpses I believe.