Had this happen during construction once. 2:1 gearless double wrap TK equipt. We didn't have rope retainers on yet. The car was on the buffer, ran the wrong direction, it picked the counterweight, the ropes on the car sheave slacked about 2' and crossed up in every possible way. Then traction broke and pulled the ropes tight in a rats nest on the car sheave. Maybe 35 floors of rope was enough weight to keep traction for a sec. Never ran a car without rope retainers again!