This is obviously a situation in which the crank sensor is not the fault. The odds of getting 4 bad sensors are so close to zero that it should not even be a consideration.
There’s not enough info known (codes, symptoms, any damage to the sensors, etc.) to make much of a guess but if the problem is actually in the crank sensor circuit then possibilities could be a faulty connector, the wire harness itself, or possibly the ECM.
One thing they’re not going to do though is take the car back.