I have an update on this. Ladders are not the only reason this happens, but they do tend to increase the odds of this problem. While in an area with lots of ladders, my companions did not follow my party leader, and therefore died to a trap while running the wrong direction around the area as the party leader descended the ladder. Again, this doesn't only happen due to ladders though, but it seems to make it worse.
Unhooking companions and controlling them one at a time is not a real solution. This is unacceptably tedious, and it also makes some characters lag far behind if a combat encounter occurs. Can companion "wandering" just be entirely disabled so they just follow the leader directly as in previous games?
