Well, first, I'd guess you aren't doing everythin exactly the same

You probably did something "right" the first time, but missed a step when you redid it. (This happens to me anyway.)
Anyway, for the two problems:
Did you add your follower to the Follower Alias or are you using custom packages? If you are using your own AI Packages for following, make sure you add them to the AI Packages for your actor and check the conditions and make sure nothing is over-riding your package.
The second follower that tries to kill everyone sounds like the Aggression level is maybe Very Aggressive or Frenzied. Check that in the AI Data tab of your actor.
HTH!