First video to present a reliable method:

I did some testing today. updated mechanics:

To trigger the glitch on any elevator in the game press floor buttons in the following order: s -> a -> b where s is the floor the elevator is currently on and a and b are other floors. Neither a nor b can be equal to s or a locked floor :(

The first two buttons must be pressed quickly one after the other . The third button can be pressed at any time on the ride before the elevator has reached a.

At that point the doors on the elevator and those on floor a reset into an open position, close, then open again and stay open until the next time the elevator is used. The elevator will then head to b. If a=b that means that on arrival the doors will be open and you can leave the elevator immediately. If a!=b the elevator will not stop at a but go straight to b (even changing direction if s is between a and b).

As soon as the doors start opening after pressing b the game thinks you have arrived at a and gives you a reset point on that floor, additionally speeding up all elevator rides where you don't need to carry an item with you and dramatically speeding up long elevator rides in the tower.

When you're moving up in the elevator with the doors open you can press against the elevator cage and block the elevator from moving at two specific point on each floor. When you are moving down instead of blocking the elevator you get pushed back. I haven't found a use for this yet.

If a is between s and b, when you pass a the doors will be open and you can exit the elevator while it is still moving. From there you can drop on top of the elevator (if you were moving down) or down to floor 6 (if you were moving up). Unfortunately you don't seem to be able to do anything there either.

It would be absolutely amazing if we could somehow break out of the elevator between floor 3 and 5. Then we could get the star on 3 without having to enter 5 (and possibly 4). We could then skip 14 additional red sigils (26 if we skip 4 too) for a total of 23 (35) sigils skipped in the messenger category, which would place it well before trancendence.