Strahd, how does K61 (elevator) work

 https://www.reddit.com/r/CurseofStrahd/comments/bcsefe/elevator_trap_spoilers/

If the elevator activates, it zooms to the top of the castle at lightning-speed, ending just under K47 which is the room with the Rug of Smothering and the Guardian Portrait. The only way out are the two trapdoors (one above the elevator that opens downward, and one in K47 that opens upward) between them.

Anyone who got caught in the elevator can only take 1 round to act before the elevator reaches the top, but everyone inside has to make a Con save against magical sleeping gas (Elves are immune due to Fey Ancestry). If they try to open the trapdoor and stand on top of the elevator when that round finishes, they need to make a Dex save to avoid getting crushed.

The trap isn't actually really threatening considering anyone who avoided it can use the stairwell next to the elevator to rush up from K61 and reach K47, fight the Rug and Portrait, and get to the trapdoor. It's just intended to split the party and cause a panic.

If you really want to be evil and mess with the party, you can rig the trap's trigger condition to additionally have it activate on the "2nd to last person to cross through" via the manual lever in K31, accompanied by Strahd's evil laughter. My campaign did this, even though the party passed Perception to learn of the trap's existence and later harshly interrogated Cyrus because of how suspcicious he was in that specific corridor, with the split further enforced by 3 allied NPCs prioritizing the Chapel over the trapped party member. Everything was played out all on a single initative tracker as one group fought the Gargoyles in the main hall and the other with Rug + Portrait, but in the end they were still able to rescue and reunite.