In the Forget About Season chapter, at the end of the map bm_c3a2a (so after the firefight with the assassins) there is an issue with the elevator.
After I push it’s button, it starts descending as it should. However if I don’t stand on the elevator when the next map (bm_c3a2b) is loaded, the elevator will go up and not down. This bug is always triggered when I am either in mid air, because I jump right before the map load, or I just stand on it’s edge on a metal corridor.
…and since the button can not be used again, this bug effectively traps the player on the top.