Noise but no Movement with 3+ Steppers & TeensyStep

#include <StepControl.h>

Stepper M1(23, 22), M2(21, 20), M3(17, 16); // create 6 motors
StepControl<> controller;

void setup() 
{
  pinMode(LED_BUILTIN,OUTPUT);
  delay(100);
  
  Stepper* motorSet_A[] = {&M1, &M2, &M3 };  // define an array of pointers to motors 1,2,5 and 6
  M1.setTargetAbs(200);                            // set targets for the motors
  M2.setTargetAbs(-500);   
  M3.setTargetAbs(-100);
//  M4.setTargetAbs(30);  
  controller.move(motorSet_A);                     // move all motors in the array to their targets

  delay(500);                                      // just to generate a nice output on the logic analyzer
 
  Stepper* motorSet_B[] = {&M1, &M3};         // another set of motors;
  M1.setTargetAbs(-110);
  M3.setTargetAbs(50);   
  controller.move(motorSet_B);                     // move set B to target

  delay(500);                                      // just to generate a nice output on the logic analyzer
 
  for (int i = 0; i < 4; i++) {                    // loop through all motors in motorSet_A...
    motorSet_A[i]->setTargetAbs(0);                // ... set targets to 0...
  }
  controller.move(motorSet_A);                     // ... and move home
}

void loop(){
  digitalWriteFast(LED_BUILTIN,!digitalReadFast(LED_BUILTIN));
  delay(100);

}

 for (int i = 0; i < 4; i++)  <=== you only have 3 motors in the array, so this loop will write to the nirvana
{              
    motorSet_A[i]->setTargetAbs(0);            
}