Within the quest area, there is a specific location near the exit of the first set of pitfalls where an unseeable pitfall will take players into the next "Fall area" near the end of the quest. I'm not sure if this is intended, as it separates the group drastically.
I'd need others to confirm this, as I have no screenshots of it happening, but I can more or less point out the area where it happens.
[hide]https://imgur.com/a/k4SjFx3[/hide]
So.
There is a bug as old as time with NWN where waypoints, traps, triggers etc can get triggered early when walking in certain directions. As I understand it its like your character bugs forward along its path and triggers stuff it shouldn't.
It happens with traps most visibly but its a NWN issue, hard coded. There isnt actually a trap in that area (And I'm sure if you run over where they were lost again then you would almost certainly not trigger it again in the same spot)
There is, unfortunately, nothing that can be done about it :<