Same C920 + MX250 setup but model retrained with blur. Further, focus and exposure were set manually as below. Slowly getting there!
cap.set(cv2.CAP_PROP_AUTOFOCUS,0)
cap.set(cv2.CAP_PROP_FOCUS,25)
cap.set(cv2.CAP_PROP_AUTO_EXPOSURE, 1)
cap.set(cv2.CAP_PROP_EXPOSURE,38)