Seen this a lot. Mostly when people in the fireteam are on different steps of the quest and/or have already completed it. This is not a guaranteed work-around, but what occasionally worked for us was to let the person who needed that puzzle be the host of the team (fireteam leader), and to let them lead the way into every encounter. (i.e. the person who needed the puzzle would be the 1st one into every load zone while the other two players stayed way back, or just left the fireteam and rejoined after the lead got to the rally flag). Probably less than a 20% success rate, but it's still better than zero%. The only method that seemed to work consistently was to run the dungeon with players on the exact same step, or to run it with players that have never stepped foot in the dungeon.