I have the setting for people to stay in the lift on true, but I can still move out of it when i hold the walk button long enough. I do get the message that you cannot leave a moving elevator.

Its a 1x1 Lift. Havent checked if it also happens with bigger Lifts.

Using:
CB 1.7.2-R0.2 Beta Build
Lift V46

Errors: None

Are players able to fly after they leave the lift?

Edit: I think I found the issue -- however trying to fix it is going to be another matter.

I just tested it myself. In both creative and survival (fly enabled) you are able to drop out of the lift and fly.

If its too much trouble I'll just have to put some glass around the lift so players can not get out of the 'box'. I was just trying to get them down from my first spawn high in the sky so they could look freely look around. Glass will do for now, I just wanted to inform you.

I had to change the behaviour of prevent leave, now it will teleport a player back into the shaft instead of just cancelling the move event. This will be in version 47

Thank you :-)!