IWT fails in general, regardless of ISBoxer, especially in ZF.

There is something about the subtle rises of the ground in there that will cause the pathing algorithm to fail and your guys to just stand still. There are a few other old world instances where this fails also, but none as bad as ZF. It also has failed on me in a few of the Outland instances, but never any Northrend instance.

What I do in the cases that I press my hotkey for IWT and my guys just stand there like idiots, is to just press my /follow key to bring them in. If they aren't quite where I want them with that, I try IWT again now that they are closer to their target. Sometimes they then path correctly, sometimes they just barrel on by their target, and I have to hit /follow again to bring them back.

It is very annoying, but again it isn't ISBoxer. It is Blizzard's buggy pathing algorithm.