I pretty much have the same problem. At least it sounds like it. My wife, who can cast spells, is in a separate stack from my Sovreign. When he casts the Teleport spell, it works fine. When she casts it, I choose the destination, I hear the sound effect, mana is drained, but she nor the units in the stack move. Even when she is by herself she will not Teleport. I suspect this happens when any character other than the Sovreign casts Teleport.

I'd like to know how to change who leads a stack. Much better to have my daughter or son leading them than some random guy.

I've got the same issue but its seemingly random, sometimes if I move them 1 space and then cast the spell it works.  I also notice I can't teleport out of a city, I always have to move out one space then cast the spell.