Ancient Vampires: Not draining life

[eXeel]

I had 75 ancient vampires which worked well, as they revived themselves.
Now I was in a battle where they didn't do it. Is it only the first few turns, they can ress themselves, or what creatures CAN'T they ress against? Is it just against human and elf and dwarfs?

Another thing is, why can't I purchase new bats? I have Ancient Vampire (Bat) and I want to buy Ancient Vampire (manform). I tried changing them in combat to man, but show as bats outside of combat anyways. Nothing to do about that? Isn't that a bug?