My friend used the elevator today. He tried to move while running it, and ended up flying around without able to jump or go back. So i had to delete his playerdata to make him normal again.

Here is a screenshot:

Yeah, it turns off player gravity to keep the server from kicking players for flying. Unfortunately, it's difficult to tell when a player gets stuck somehow. Using the elevator again usually gets you unstuck.

Maybe just add an admin command to undo it in case this happens?

That should help. I was thinking of adding a listener for if the player logs out while using the elevator, but I'm not sure how well that would work. Maybe I could store a list of entities in the elevator when it starts moving, and make sure they stay in.

Oh forgot to close this one, solved this issue a few versions ago, if you left click the air it resets gravity for all entities in the elevator.