I am noticing that, in Scene three, when you gain Crossroads Keep, that the AI will shut off in the last member of any group. Even though 'Puppet Mode' is off and the follow distance can be set to 'near,' one member of your group will stand by the portal, hanging their heads slightly as if forlorn. They will not move from the spot, even if a battle is going on and, when you take control of them, everyone else will (unless in battle) run back to follow them. This is starting to turn any adventure into pushing a chain.

Has anyone else had this problem, and how do you fix it?

Have you tried just telling them, follow me, or guard me?

NW2 works off of behavior settings from the character screen. From there, you can activate the AI and set the follow distance and guarding functions. There really is no other way to 'tell' the other characters anything, and they usually follow in the wake of your activated character like kites on a string.

I think you'll find that if you right click on the troublesome companion (or their portrait)
and choose "issue command" you can tell them to guard you & that often fixes the unresponsive AI you are having trouble with.
Selecting the party & choosing "stand your ground" is handy if you don't want them running over traps before Neeska has disabled them.
To talk to your whole party, right click anywhere on the screen & choose "broadcast command"