Yup, it's been like this for quite a while now. You'd think it being a part of one of the "Main Quests" in the game, that Bethesda would have fk'n fixed this by now.

But I digress. Your best solution when you get stuck in this quest (and there are 2-4 different spots where the NPC's will get stuck) is to fast travel outside, back to the cave entrance where you entered the code on the keypad, then walk back in and head to where they got stuck.