[Python] Haar Cascade classifier freezing code's execution

Trying to use Haar Cascade classifier, the program stops indefinitely using this code:

import cv2

haar_file = cv2.data.haarcascades + 'haarcascade_frontalface_default.xml'
face_cascade = cv2.CascadeClassifier(haar_file)

# Reduzindo resolução
webcam = cv2.VideoCapture(0)
webcam.set(cv2.CAP_PROP_FRAME_WIDTH, 320) # width
webcam.set(cv2.CAP_PROP_FRAME_HEIGHT, 240) # height


while True:
retorno, frame = webcam.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
print("Grayscaled")

faces = face_cascade.detectMultiScale(gray, 1.3, 3, flags= cv2.CASCADE_SCALE_IMAGE)
print("Faces detected")

for (x1, y1, x2, y2) in faces:
moldura_face = gray[y1:y1+y2, x1:x1+x2]

cv2.rectangle(gray, (x1, y1), (x2, y2), (0, 255, 255), 2)

moldura_face = cv2.resize(moldura_face, (48, 48))

# cv2.putText(im,prediction_label)
cv2.putText(frame, '% s' % ('prediction_label'), (x1-10, y1-10),
cv2.FONT_HERSHEY_COMPLEX_SMALL, 2, (0, 0, 255))

cv2.imshow("Output", frame)
cv2.waitKey(27)


I tested the webcam with a simple opencv code and it works fine, even with a ball detector code using HoughCircles, and it works fine.

But when executing the code above, it only gets to:

[...]/testCascade.py
4367ea-dec2-446e-99c4-7ea97825c9c3
Grayscaled


And never reaches "Faces detected"

I don't understand why, I tried reducing the code as much as possible but I still can pin point the problem. Can anyone?

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