At a random point when playing with friends, doing missions all of a sudden this bug appeared. At first, no players could exit any vehicle and the only way out was death. The players would show as (animation wise) being out of the vehicles, standing up on the bench of helicopters, crouching in the driver seat of trucks etc.

Screenshots use CUP and RHS but bug persists without. . However there are also times where they can get in and out of the vehicles on their screen, but on the servers side and most other players screens (most because sometimes other people can see other people normally for some reason). Because of this the player in question can preform any normal action, shooting, grenades, healing, whatever and those actions affect other players. The player that is bugged is invisible and can go around killing all other players being unseen. The people that are bugged can be killed by shooting them where they are on anyone elses client, usually in the vehicle they got in.
It seems to be at random whether or not the person gets stuck or can get out of the vehicle.
What makes this weirder is that I am unaffected, with people seeing me entering and exiting vehicles when I am hosting. Also tried with different people hosting the server with the same bug.