Raspberry Pi PWM control becomes affected when I combine it with FLASK - raspberry-pi

Question

Im trying to implement a control using Raspberry Pi's PWM. I had success controlling the intensity of a LED with the following code:
# Pin Definitons:
pwmPin = 18 # Broadcom pin 18 (P1 pin 12)
# Pin Setup:
GPIO.setmode(GPIO.BCM) # Broadcom pin-numbering scheme
GPIO.setup(pwmPin, GPIO.OUT) # PWM pin set as output
pwm = GPIO.PWM(pwmPin, 50) # Initialize PWM on pwmPin 100Hz frequency
# Initial state for LEDs:
pwm.start(10)
try:
while 1:
cycle = raw_input("Introduce Duty Cycle")
dc = int(cycle)
pwm.ChangeDutyCycle(dc)
except KeyboardInterrupt: # If CTRL+C is pressed, exit cleanly:
pwm.stop() # stop PWM
GPIO.cleanup() # cleanup all GPIO
Then I wanted to control the LED brightness through a web page. For that I used FLASK and the previous code. When I set the Duty Cycle from the web page the LED brightness change accordingly but it fluctuates randomly.
It's a strange behavior and I dont know why it is happening. Right here the code implemented on FLASK:
# Pin Definitons:
pwmPin = 18 # Broadcom pin 18 (P1 pin 12)
# Pin Setup:
GPIO.setmode(GPIO.BCM) # Broadcom pin-numbering scheme
GPIO.setup(pwmPin, GPIO.OUT) # PWM pin set as output
pwm = GPIO.PWM(pwmPin, 50) # Initialize PWM on pwmPin 100Hz frequency
# Initial state for LEDs:
pwm.start(10)
app = Flask(__name__)
#app.route('/')
def index():
return render_template('motor.html')
#app.route('/motor', methods=['POST'])
def motor():
dc = int(request.form['valor'])
pwm.ChangeDutyCycle(dc)
return redirect(url_for('index'))
if __name__ == "__main__":
app.run(host='0.0.0.0', port=81, debug=True)
pwm.stop() # stop PWM
GPIO.cleanup() # cleanup all GPIO