Conducción de múltiples motores paso a paso con Raspberry Pi

Estoy tratando de controlar dos (posiblemente más) motores paso a paso con la Raspberry Pi 3B. El principal problema que encuentro con la ejecución de dos motores paso a paso es que cuando ejecuto ambos motores, ambos parecen girar a la rotación y velocidad exactas, pero cuando solo hago funcionar uno de ellos, el motor parece girar más lentamente y Suena mas irregular. Los servomotores utilizados aquí son el motor paso a paso Nema 17HS4401 y yo uso l298n para el controlador del motor. Aquí está el código que hice para hacer funcionar los motores:

import RPi.GPIO as GPIO
import time
import threading

class Stepper:

  def __init__(self, steps_per_rotation, A1, A2, B1, B2, E):

    GPIO.setmode(GPIO.BCM)
    GPIO.setwarnings(False)

    self.steps_per_rotation = steps_per_rotation
    self.coil_A_1_pin = A1
    self.coil_A_2_pin = A2
    self.coil_B_1_pin = B1
    self.coil_B_2_pin = B2
    self.enable_pin   = E

    GPIO.setup(self.coil_A_1_pin, GPIO.OUT)
    GPIO.setup(self.coil_A_2_pin, GPIO.OUT)
    GPIO.setup(self.coil_B_1_pin, GPIO.OUT)
    GPIO.setup(self.coil_B_2_pin, GPIO.OUT)
    GPIO.setup(self.enable_pin, GPIO.OUT)

  def set_step(self, w1, w2, w3, w4):
    GPIO.output(self.coil_A_1_pin, w1)
    GPIO.output(self.coil_A_2_pin, w2)
    GPIO.output(self.coil_B_1_pin, w3)
    GPIO.output(self.coil_B_2_pin, w4)

  def enable(self):
    GPIO.output(self.enable_pin, 1)

  def disable(self):
    GPIO.output(self.enable_pin, 0)

  def forward_rotation(self, delay, rotation):
    steps = rotation * self.steps_per_rotation
    delay = delay/1000
    self.enable()
    for i in range(0, steps):
      self.set_step(1, 0, 1, 0)
      time.sleep(delay)
      self.set_step(0, 1, 1, 0)
      time.sleep(delay)
      self.set_step(0, 1, 0, 1)
      time.sleep(delay)
      self.set_step(1, 0, 0, 1)
      time.sleep(delay)
    self.disable()

  def backward_rotation(self, delay, rotation):
    steps = rotation * self.steps_per_rotation
    delay = delay/1000
    self.enable()
    for i in range(0, steps):
      self.set_step(1, 0, 0, 1)
      time.sleep(delay)
      self.set_step(0, 1, 0, 1)
      time.sleep(delay)
      self.set_step(0, 1, 1, 0)
      time.sleep(delay)
      self.set_step(1, 0, 1, 0)
      time.sleep(delay)
    self.disable()

  def forward_time(self, delay, second):
    delay = delay/1000
    self.enable()
    timeout = time.time() + second
    while time.time() < timeout:
      self.set_step(1, 0, 1, 0)
      time.sleep(delay)
      self.set_step(0, 1, 1, 0)
      time.sleep(delay)
      self.set_step(0, 1, 0, 1)
      time.sleep(delay)
      self.set_step(1, 0, 0, 1)
      time.sleep(delay)
    self.disable()

  def backward_time(self, delay, second):
    delay = delay/1000
    self.enable()
    timeout = time.time() + second
    while time.time() < timeout:
      self.set_step(1, 0, 0, 1)
      time.sleep(delay)
      self.set_step(0, 1, 0, 1)
      time.sleep(delay)
      self.set_step(0, 1, 1, 0)
      time.sleep(delay)
      self.set_step(1, 0, 1, 0)
      time.sleep(delay)
    self.disable()

  def forwards(self, delay, steps = 1):
    delay = delay/1000
    self.enable()
    for i in range(0, steps):
      self.set_step(1, 0, 1, 0)
      time.sleep(delay)
      self.set_step(0, 1, 1, 0)
      time.sleep(delay)
      self.set_step(0, 1, 0, 1)
      time.sleep(delay)
      self.set_step(1, 0, 0, 1)
      time.sleep(delay)
    self.disable()

  def backwards(self, delay, steps = 1):
    delay = delay/1000
    self.enable()
    for i in range(0, steps):
      self.set_step(1, 0, 0, 1)
      time.sleep(delay)
      self.set_step(0, 1, 0, 1)
      time.sleep(delay)
      self.set_step(0, 1, 1, 0)
      time.sleep(delay)
      self.set_step(1, 0, 1, 0)
      time.sleep(delay)
    self.disable()

luego ejecuto el código como una clase en el siguiente código:

from Stepper_Motor import Stepper
import time
from threading import Thread
from queue import Queue

Acoil_A_1_pin = 2
Acoil_A_2_pin = 3
Acoil_B_1_pin = 4
Acoil_B_2_pin = 14
Aenable_pin   = 15


Bcoil_A_1_pin = 18
Bcoil_A_2_pin = 17
Bcoil_B_1_pin = 27
Bcoil_B_2_pin = 22
Benable_pin   = 23

steps_per_rotation = 50

stepper_A = Stepper(steps_per_rotation, Acoil_A_1_pin, Acoil_A_2_pin, Acoil_B_1_pin, Acoil_B_2_pin, Aenable_pin)

stepper_B = stepper = Stepper(steps_per_rotation, Bcoil_A_1_pin, Bcoil_A_2_pin, Bcoil_B_1_pin, Bcoil_B_2_pin, Benable_pin)

#q = Queue()
motor_on_A = False
motor_on_B = False

def spin_A():
    while True:
        if motor_on_A:
            stepper_A.forwards(2)

def spin_B():
    while True:
        if motor_on_B:
            stepper_B.forwards(2)

def control():
    global motor_on_A
    global motor_on_B

    while True:
        user_input = input()

        if user_input == "start_A":
            #q.put("start")
            motor_on_A = True

        elif user_input == "start_B":
            #q.put("start")
            motor_on_B = True

        elif user_input == "start":
            #q.put("start")
            motor_on_A = True
            motor_on_B = True

        elif user_input == "stop_A":
            #q.put("stop")
            motor_on_A = False

        elif user_input == "stop_B":
            #q.put("stop")
            motor_on_B = False

        elif user_input == "stop":
            #q.put("stop")
            motor_on_B = False
            motor_on_A = False


sA = Thread(target = spin_A)
c = Thread(target = control)
sB = Thread(target = spin_B)


sA.start()
sB.start()
c.start()

Soy nuevo en programación y electrónica, por lo que agradeceré cualquier ayuda,