its called a rollback, its when every brake on the lift fails at once and gravity just like, takes over man
Especially since the one side is loaded with people and the other isn't. There should be a giant weight that you pull a pin on and slams a clamp shut on the cable. It isn't really safe either since it supposed to cause the lift to stop instantly, it's more for if you lose all ability to power the lift and want to stop a rollback from happening.
But for a rollback like that to happen no regular maintenance had been done for a while.