yep there should always be dual systems in place for normal brakes brakes if 1 of them fails to act it should fail safe in a way that applies the brakes , hand brake should be isolated Independent system from the normal brakes and this is a massive fail linking both of them in this way
coaches from years ago even have backup E brake handle just in case for some reason the air brakes lock the brakes open state (practically nearly impossible, but nearly is not good enough with more then 50 people and no seatbelts), you just push it down and it overrides the air brakes by forcing the brake clamps directly via a motor
Biting the hand that feeds IT
